I don't get your point.
I understand that for general testing a Orthochromatic film is the lesser choice as it does lesser disclose chromatic abberations than a panchromatic film. But then again colour filmn is the best choice for such anyway.
But I do not undertand why orthochromatic film is not apt for just checking a reassembly of a lens.
Well that was kind of my point. It is perfectly fine for testing a lens after assembly,
if you remember to run further detailed tests against chromatic aberrations.
That is, assuming you use pan films at all at least. If all you're using is ortho films, and your focus tests pass with that film, then you're good to go - If you're never measuring anything towards the red range, then you don't have to care whether or not it is in focus.
If you allow yourself to be overly focused on too narrow of a range while testing, then it becomes easier to overlook errors or flaws. Depending on the camera and focusing system it can be easy to dismiss your initial thoughts that the 'best focus' you could achieve seemed a bit soft or weird if you put too much faith in your testing method without considering its short comings. "The image looks sharp under a loupe on film..." is a good way to reinforce in your mind that everything is fine. After all, a small aberration can be hard to see in a view finder if you're not actively testing for it, but still be enough to muddy enlargements.
I learned this lesson 'the fun way' at a job years ago thanks to part of the calibration on the big lenses we were using relying on some big sheets of film with a narrow response range. [I think it was some kind of xray film.] Using it let us record the entire image circle in one go to use as part of the baseline tests that everything was aligned correctly. System in question was designed to use one or more small sensors that could be moved around within an oversized image circle.
Film tests of 'the whole image circle' passed, but were failing when run against the smaller sensors. Eventually tracked it down to a flipped cell. The few elements in it didn't do a lot to the light, but the right way round was supposed to make some minor correction, while the wrong way round just made things 'a little bit worse'.
Turns out one of the engineers had stated that the "Big obvious arrow" engraved on the otherwise symmetrical subassembly barrel pointed towards the 'target', as in where we were targeting the light to be collected... While another engineer had understood that 'target' was the thing we were pointing the camera system at...
In short, it is hard to see errors that you're not actually looking for if they're small enough.
Another great lesson learned from that project is that being the only native English speaker on a team officially communicating in English can be very fun and 'interesting'.