Question about straightening the pins of a resettable polyfuse
For manual assembly, you don't want to distort the leads so as to crack the epoxy case seal (long term reliability problem for contamination and stress cracking of lead to body attachment points)  If your hole size and spacing is correct this shouldn't be a problem; if you need to re-form the leads try to do it in such a way that the seal doesn't crack by using two needlenose pliers for example.  If this is a one-off project with no service costs, then those rules can be relaxed as you see fit.  

Automated lead forming through hole components allows fast and accurate machine placement, and there are still services that provide custom forming (axial to radial for example) and re-taping.  

Through hole component assemblies are generally run through a wave solder machine, and forming/staking the leads help retain the correct position preventing components shifting, tilting, sliding up/down.  

In the case of a PTC, the goal is get a repeatable position for thermal environment (you don't want 5% of your production lot parts leaning against a hot transformer for example) and for the aforementioned epoxy seal integrity.