I did not.
I am just realistic.
Unlike you, who wants the best hardware at a bargain bin price and thinks a Vita 2 would be great idea for Sony.
The Steam Deck is impressive for what it is, but it's not a platform to play an AAA next gen game releasing in 2025.
Obviously you could run the game on the Deck, it's a PC after all, but GTA 6 would run like the Switch version of Ark. If you're lucky.
I could also run GTA 6 on a GPD WIN, but it would run like garbage. The hardware isn't built for games like that.
The games (Witcher 3, Doom etc.) you probably talking about run at 27-30 FPS with dips, which is far more playable than 20 FPS with dips. Only the worst offenders like Ark run at 20 FPS or below and its universally agreed upon that Ark is a terrible game on Switch.
GTA 6 on the Deck wouldn't run at 27-30 FPS, which is comparable to the performance of GTA V on Xbox 360, it would run far far worse, close to unplayable perhaps.
20 FPS is a rough estimate, the correct performance is probably below that.