Not all levels force you to save the maximum possible %, not even in Psycho.
(Based on current positions, which may change, and all are assuming no backroutes are used, whether via glitch or not)
Psycho 6 (The Bulldozer) requires 98%, but 100% is possible.
Psycho 9 (Coalburner) requires 80%, but 92% is possible.
Psycho 23 (The Framework) requires 90%, but 94% is possible (while theoretically, 96% can be done, I've yet to acheive this, and I've tried heaps, so it may be impossible to line up the perfect timing for this).
True, that's only 4 levels (including No Salvation) out of 19 Psycho levels so far, but it still makes the point.
There are varying reasons for this. No Salvation is simply following the pattern of requiring an extra 10% in each incarnation of it. Coalburner has nothing to gain from making the save requirement steeper, so it simply doesn't do so. The Framework needs that flexibility - while 92% or 94% is definately possible, it's extremely hard to get anything over 90% (and that in itself is quite tricky, you'll probably have at least one or two 88% or possibly even 86% attempts before you make it). The Bulldozer is the worst of all - it gives you a blocker, and lets you lose one lemming, most likely making you assume the blocker is somehow involved in the solution. It's not, and in fact, you should be acheiving 100% every time.