I think a couple of things are going on here. First, tire manufacturers are making tighter beads that are harder to get over the edge of a rim. Second, the tubeless compatible rim profile has a less deep “well” (further complicated by the fact that the well may be partially filled with tape) and the well (the smallest diameter portion of the rim) is narrower because of the shoulders in tubeless rim profiles. These things all facilitate seating a tubeless tire, but may make getting the tire on and off the rim heck.
The classic answer to a tight bead was to get the beads in that well all the way around the rim, which would free enough bead to get it over the sidewall of the rim. That is harder to do with the narrower and shallower wells of tubeless rims.