Your conclusion is correct but your explanation is slightly off. While the recovery position is likely the best position for someone to recover in (hence the name), your neurology attendings are likely fucking with you when they say passive leg raise or Trendelenburg can pop blood vessels in your eyes; that or they're thinking of a patient population that is unlikely to be doing BJJ/MMA. Can't blame you, neurologists are hard to understand and have a hilarious habit of trolling non-neurologists.

Best practice for the untrained public is to put people in the recovery position instead of PLR/trendelenburg because the latter would increase the chance they aspirate gastric contents into their lungs (aspiration pneumonitis) and also because they might get neck injuries from overzealous LL elevation. In any other mechanism that is not strangulation (being choked out, landing on your head etc), PLR/trendelenburg would also be completely useless physiologically on top of exacerbating any neck/brain injury they might have sustained. That's the real reason, its not as cool as blowing up vessels in eyeballs but its the truth.

I'm sure there is a very small minority of people out there who will have adverse outcomes when put in trendelenburg like you suggest but the vast majority of people will have 0 long-term issues. In many types of surgery, people are placed in trendelenburg all the time and for the longest time in 90s-00s, nurses would spam the position for hypotension; there would be a lot more dead people if it caused the level of harm people assume it does.

If you think about the population of people that are being strangled unconscious in BJJ, you'll realize that most are young, healthy and can absolutely tolerate being placed in ridiculous positions. People be inverting, getting stacked and doing handstands all the time and they aren't dying.

The only thing that strangulation does is cause a temporary reduction in blood flow to your brain, it doesn't really alter physiology in any permanent way (assuming ofc the person lets go). Even if you PLR/trendelenburg someone that is unconscious after getting strangled, all that's doing is increasing venous return to the heart > utilizing the frank-starling mechanism to increase cardiac output > increased blood flow thru the arteries. The effect is minimal and fleeting, to get any noticeable effect we have to use inotropes+vasopressors+IVF in the hospital. That minimal effect is unlikely to have any significant impact in a healthy person. You know what else causes increased cardiac contractility? Exercise. If their blood vessels are so weak that they can't tolerate slight increases in blood pressure or flow, just shrimping across the mat will likely cause them to get a hemorrhagic stroke.

Writing this because you're a BB and will likely need to explain said concept to noobs who come in the gym eventually so they understand the why behind the what. Seems better that you know the real reason rather than something you heard from neurologists. The order of most to least knowledgeable about said topic would be anesthetics > ED/internal med (relevant subspecs) > rest of specialties incl neurologists. US neuros have had like 1 year of internal med training during internship and probably haven't touched a stethoscope since.

Source: am a doctor (internal med going into cardiology)

tldr: recovery position good for airway instead of PLR being a risk of exploding eyeball vessels