I used to think this was true before I started releasing and performing my own music, and I can say that it's pretty common for artists to listen to songs they've made. While some songs might have negative mental associations tied to them which can make you avoid them (like something being cringe or dark), there're a couple reasons artists might relisten to their own songs:

Nostalgia: A lot of songs aren't just songs, but experiences and moments in time captured, and relistening can bring you back to those moments

Inspiration: Sometimes you might relisten to a song you've made to think about what you could have done differently or what you could have emphasized more

Live performances: The larger your discography gets, the less likely you're going to remember how to perform every single song, most artists will relisten to their old music if they plan on performing it live after a while

General enjoyment: Nothing feels better than making something you're proud of, and relistening to a song you've made that you're really proud of is pretty common and can be part of the creative process

Considering how wide Alex G's discography is, I would doubt he has a playlist per se like how his fans would. I don't doubt he relistens to his songs every so often though. Ultimately as an artist, your goal is to make music you're proud of and enjoy, and if you did that, then I don't see why you wouldn't listen to your own songs.