I'm fairly sure the correct answer is: It depends, but most likely yes.
Springs can take a certain force without being permanently deformed. The springs on tools are of course designed to not deform permanently during normal use, and will thus pass through the 45 degree position during normal use without any issues.
However, the force a material can withstand without deformation over a long time is less than the force a material will happily withstand over short time span. If exposed to a force over a long time the material can start to creep and slowly deform. This is the reason why designers strive to make sure springs are normally in a relaxed or low force position. Different spring materials have different charachteristics, but multitools are very unlikely to be made of anything particularly resisting or exotic.
A spring can be made strong enough to resist creep for a given force. That will require more material, weight and cost though - all enemies of multitools. And because most multitools will only be in 45 degree positions for a short transient time chances are that the spring are not designed to resist creep over time in that stronger force position. So my answer is that creep is likely over time - how much time is hard to tell.
Hopefully that was somewhat coherent?