could be you're talking about 2 drinks and I'm talking about 6. IDK.
there are probably exceptions to everything; maybe you are one. in the end, what difference does it make? I doubt anyone can find health reasons to justify more than a single glass of red wine (not liquor, not beer). even if it is the reason for your lower ahi, the vast array of other negative effects will very likely outweigh any such benefit.
there may be other reasons for lower ahi's. they say that once the buzz wears off you're more likely to wake up. I know from my experience that my best ahi's are when I don't sleep very well, never sleeping deeply enough to produce much apnea.
IDK, tiredPerson. you can find a great deal of help to optimize your pap therapy here. but I'll be surprised if you find much support or even explanation for alcohol making sleep and apnea better. I'm open to persuasion though. I miss my Guinness.
btw, unless you have one of a few specific conditions, you may never know what causes your central apnea. I was diagnosed with 100% central in 1987. no clue why other than something must be broken in my brain. never was offered treatment for it either. not even in 2016 when I scored nearly equal centrals and obstructives during my sleep study. they called it obstructive and prescribed me a machine that doesn't treat centrals. only after taking matters in my own hands and buying a used asv has my central index dropped below 5.
I used to try and figure out why I like drinking so much. all that did was enable me to put off quitting. It wasn't hard to quit and I've had a few drinks on special occasions since then so I know I wasn't helplessly hopelessly addicted. I think of it as a habit. for me, it's just easier to avoid than manage that habit. maybe you don't need to cut it out of your life but as I said, I think you will be hard pressed to find an explanation for how or why alcohol leads to fewer apnea.
this is not intended to be rude: we all need to do whatever works for us. if it's working for you, and to support the idea it's not simple coincidence, you could keep it up on a regular basis and see if fewer apnea continues over time. like I said, I'm open to persuasion, not that you need to convince me.
an afterthought: for years I took generic adderall for ADD and the effects of apnea. the best sleep of the night was always for about 45 minutes after I took my morning adderall, before it kicked in enough to keep me awake. I could never explain that and my doctor looked at me like I had two heads when I mentioned it to him. coffee too. I love to nap for 30 minutes or so after my morning cup of joe. again, it's the most refreshing sleep of the night. maybe similarly, I believe I also drank - self medicated - because it made me feel better and allowed me to focus on mundane things for a little while before it made me stupid. there did seem to be a short window with alcohol and adderall that seemed to even something out for me. maybe simple relaxation. unfortunately whatever positive effects I may have thought I got from these things never lasted long enough to be very useful and the negative effects always won the day.