You mention "all sorts of COVID-restriction" when referring to LHR. Whilst of course 8 hours within LHR isn't great, in terms of COVID restrictions, if you're just transiting through LHR, there's absolutely no restriction whatsoever, no need to fill in a UK PLF either! In fact, provided your passport/nationality permits you to do so, you could even go into Central London comfortably and enjoy a light meal or some shopping entirely restriction-free and mask-free, all you would have needed is a UK PLF completed in this case (I say this assuming you're fully vaccinated). Also, if your passport/nationality didn't permit entry into the UK, even then, particularly if you're transferring onto "another OW carrier" from LHR, I would suspect the likelihood is that this would have been from T3 (as it isn't seemingly QR or BA and most certainly won't be AA either as you're not travelling back to US from the US, which leaves behind RJ, QF, MH, CX, AY) which would have permitted you to the superior CX and/or QF lounges in T3 (and BA T3, though why one would want to choose that over the others is puzzling) if you were booked in J (irrespective of status). Of course, you've not been wishing to disclose your final destination, which is absolutely fine, but irrespective, the LHR routing may indeed have been a pretty reasonable option. Nonetheless, you still ended up getting QR J which even without Qsuites is still a far superior hard and soft product compared to many other airlines! So IMO, whilst the back and forth wasn't helpful, particularly given yours was an award ticket also, I believe you have done quite well!
Safe travels.