I haven't explained myself properly. In the formula for PSR 'O' stands for groundspeed out to PSR. In the formula for PET 'O' stands for groundspeed onwards from PET. Assuming TAS and wind components are the same of course then these two speeds would be the same. But this is not necessarily the case, for instance we could be calculating an engine failure PET where the speed out to PET is based on an all engines TAS and the speed either onwards or back from PET is based on an engine out TAS, perhaps at a completely different height. Its a common mistake to assume that, because both formulae use the same letter 'O' that the two formulae can be related. The examiner has made this mistake.
I did not mean that O=H, I meant I assumed, as the examiner seems to have done, that the O in the PSR formula is exactly the same as the O in the PET formula. Likewise in order to get the answer I have assumed that H has the same value in both formulae, and it need not have.