I do understand what your saying. However it is a reasonable, valid and fair question.
Changing the operating angle from 0 to 80 degrees completely alters the stress / strain distribution, Can’t really expect a machine to perform the same way in a near vertical position without validation.
No one is asking for documented proof, test results etc… Just a rough description, i.e. analysed where the stresses are (FEA?) and tested those components (if not the full machine) to simulate those stresses over a suitable length of time then post analysis for wear level, fatigue damage, machine accuracy etc…
The people who have asked this question are fully behind 1F and no doubt love to sing its praises outside of this forum. They also appear to know their stuff in the engineering world and are asking due to similar experiences. I’ll submit the question to 1F support.