Phoneutria is a wonderful piece of ICE from so many perspectives. I'll cut to the chase--it is very Jinteki. Let's break it down.
Saisentan, long the replacement for Komainu, is the ICE I enjoy using as a baseline for Jinteki sentries these days. If we completely ignore the text on both Sai and Phone, they are quite comparable. Sai costs 5s and has three "1 net damage" subs, whereas Phone costs 4s and has two. Strictly from a -to-net-damage ratio, Sai (0.6/) has Phone (0.5/) beat. That being said, sometimes a 's difference in rez cost makes all the difference, and there are times where you might be willing to take the lower ratio for the lower cost. Both ICE are Str 2, so they're on equal footing there.
Now, let's look at the text.
Sai has the potential for bonus net damage by playing the card-type guessing game and the statistics in Spaulding's review of Sai shows that this can be quite favorable for the corp even without prior knowledge of the runner's hand. However, this is only if the subroutines themselves fire. Subs typically only fire against a face-checking runner--but we'll get to this in a moment. Onto Phone, the damage caused by a face-check is far less deadly. The sum total net damage will be 2 and always 2. While this may bring a runner down below 3 cards in hand (the magic number for a snare flatline) there won't be that many cases where this can actually threaten a net damage kill. Frankly, if the runner is blind-running a server against Jinteki with only 1 card in hand, please take them aside and kindly point out that there might be better ways to approach the situation.
So what does Phone actually do then? Some may be tempted to say "it can give the runner a tag if the runner has 4 or more cards in grip when they pass it," and while from an academic perspective they would be correct, it misses the far greater and insidious nature that makes Phone a wonderfully designed Jinteki ICE, both thematically and mechanically. You see, Phone is a hidden mind-game.
2 net damage isn't that bad. In fact, a lot of runners, especially Anarchs, will gladly take it to save on the cost of installing a killer and breaking the subs. However, 3 is the magic number when running against Jinteki since it keeps you safe from Snare!. 3 will also keep you safe from Phone's tag--but consider that if the runner started with 3 or 4 cards in hand and they eat Phone's net damage, they're now in Snare flatline territory. So they're incentivized to actually spend the s to break Phone.
...but maybe they're a cheeky runner and they don't care about the tag. After all, you're Jinteki--you're not exactly known for your tag-punishment tactics. They overdraw to 6, make a run, take the net damage, take the tag, and crash into your double-advanced Urtica Cipher. They live just fine, they don't shake the tag (because why would they) and they undid all of your trap setup without having to spend a dime... only to die unsuspecting to your new Mindscaping card's secondary effect.
Okay, okay, so maybe they get smarter. They expect Phone, they expect Mindscaping, and they've sussed out and avoided your Urtica. They run with 5 in hand--the perfect number. They hit Phone and laugh as they eat 2 net damage, going down to 3 in hand, which simultaneously avoids Phone's tag. They crash into a server with an un-advanced Snare, live through the whole ordeal, and again, undid all your traps while spending nothing... except they now have a tag from Snare... which you can then use to flatline them again next turn with Mindscape.
But lastly, we encounter the actual smart runner. The big-brain hacker. All of this is irrelevant if they shake the tag, right? The biggest-brain runner will. They won't run last click. They won't forget to leave themselves 2s for the cost. But that is exactly the point. Phone's greatest strength isn't its net damage, or tag-into Mindscape flatline potential. It's not about driving them mad by asking them whether they want to run with 3, 5 or 6 cards in hand. It's the fact that they have to care about the tag at all, which means that (barring tag-removal shenanigans like Solidarity Badge, Networking etc.) Phone forces the runner to lose something regardless. They lose a and 2 s if they go in with more than 3 cards. They lose 2 s and 4 s if they do the same and hit a snare afterwards. They lose 2 cards if they go in with 5-6 and eat the subroutines (and probably want to shake the Snare tag if they hit one, for fear of Mindscape). They open themselves up to a flatline if they run with 4 or less and eat the subs.
Now do you remember when we were talking about Sai? (I bet you thought I forget, eh? :P ) Well, therein lies the difference between the two. Sai is a flatline ICE, used to punish face-checking runners. Phone is a taxing ICE used to mess with the runner's head.
Does any of this on its own actually concretely kill or stop the runner? No. But it's a lot for them to think about all at once--ergo, the mind game.