That your definition of player agency excludes other forms of player agency that I may have as a player in other tabletop roleplaying games.
No!
No!
No!
I do see an incredibly obvious reason: my agency that I have as a player playing in a given tabletop roleplaying may not be strictly limited to what my character does. That's why. It may not make a difference to you, but that distinction does matter to me. You said it yourself:
You're curious what my point is. Here it is. I don't know how to make it clearer.
Player agency is about what we do as players in the game. What I can do as a player playing in games like Fate, Cortex Prime, Stonetop, Torchbearer, or maybe even Daggerheart is not necessarily limited to what I can do as a player playing at your D&D 5e table. The bounds of my agency as a player playing these games exist outside of the scope of the agency I may have playing in your high agency D&D games or Bloodtide's. I think that any definition of player agency for tabletop roleplaying games must be inclusive, rather than exclusive, of all these different modes of player agency. The problem with your definition of player agency that conflates player agency with character agency is that defining player agency strictly in terms of character agency excludes these other modes of player agency that I may have as a player playing these other games. For that reason, I don't think that your definition is a good or functional one.
So your definition of higher player agency intentionally includes your games? That's convenient, if not likely circular.
But I do find it interesting that while you dislike any potential implication that your D&D games have lower player agency than other games, you clearly don't have a problem claiming that someone else's D&D games have lower player agency. So why do you have such an issue with the idea that your D&D games may have lower agency than another game, which may have things players can do to play the game outside of your own preferences? It strikes me as a bit curious, if not hypocritical.