That's not definitional, and no, it wasn't forced on you. I was unable to respond to that thread for a few days, and when I returned it had died down, so I didn't respond, but I noted that you had continued to persist to holding onto bits that weren't necessary as if they were. Skilled play doesn't require the system to be improvise, it requires that the player be able to improvise new ideas and apply them within the system. IE, skilled play means that the players have to use their smarts and improvise new strategies and approaches, but not that the system be able to extemporaneously adjudicate out-of-system rules. Skilled play can absolutely exist in games where that is the case -- like D&D, where the GM can go outside the provided system to adjudicate an action not presented within the system. But, this is not necessary. You can have skilled play without ever once altering the system, or being allowed to alter the system. Skilled Play in Blades in the Dark, for instance, while different from B/X, never requires interpreting the system into something new. Likewise, you can have skilled play in a CRPG. I mean, at the surface, making a set of characters that compliments vice one that all are the same and are very niche will have major impacts in how well you can progress the game. This is part and parcel of skilled play -- creatively leveraging the system to achieve player goals.