I know some people will never accept it, but for just $10-$15 per month, without any type of price increase, yes, that indeed does make any and all new game additions effectively free. Want to tell all Game Pass Ultimate subscribers we had to pay for EA Play when it was added at no additional cost? I mean, you could, but it wouldn't be accurate. Access to an EA Play subscription with full access to the vault of games was given to Game Pass Ultimate Subscribers 100% free of additional charge.
What surprises me often about effects to downplay Xbox Game Pass is that the very people doing so are no doubt likely Netflix, HBO Max, Disney+ or Hulu subscribers, or at the very least are taking advantage of something eerily similar. Go ahead and tell me how I've somehow had to individually pay for every episode of invincible I've watched on Amazon Prime Video, or how I've paid for every episode of WandaVision or Loki on Disney+ that I've binge watched, or how my access to HBO Max (which comes courtesy of my Verizon Fios Cable Package) is somehow costing me extra to have when it's a free perk of something I was already paying for for years. With Xbox Game Pass Ultimate I pay a one-time monthly fee, that doesn't ever increase regardless of how many new games are added, to have full access to all existing and new games on the service. And yes, so long as a game is still present on Game Pass, I actually do own it as well as every other game included, because that's what I'm paying for, access to a games subscription service.
Short version Yes, new games are added completely free all the time. And, yes, an Xbox Game Pass subscription does represent full game ownership. Telling people they don't own anything on game pass is like telling people they don't own their house because they pay a mortgage, or that they don't own the internet or cell phone service they're using because they have to pay monthly to keep it active.