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Sure. Assume that I'm fighting another player and I usually use a skill at timing A, and it's not really helping as much as usual, or I realize 'I could use this differently, but it would take more practice and careful execution timing'.
I start doing this, it's quite hard and only helps me against that player and similar characters, but it helps quite a bit, so I've gained some skill/experience without any change to my gear or skills. Then that change makes me realize something else similar to it, and so on.
Some people consider this a form of interesting progression, I've met some that thing this is a tedious waste of time/'gatekeeping'. So I don't assume when someone says 'progression', that they are including this. Sure it's just 'getting better' but the depth of it can be pretty extensive, so for some games, it is the main 'progression', depending on how you look at it.