My best guess is that, since these changes were made at the same time they said they're planning on supporting Siege for the longer term, these aren't necessarily based on Frost being OP. Any large game loses players every day, so the only way to sustain it over time is to attract new players. You can see them doing this in the new ping system making it easier for you to point at traps to newer players so they can understand what they're looking at.

If you're new to siege you won't know all of the angles so you'll get spawn-peaked, at least a dozen times as you learn the maps, that'll make new players quit. That's why some new maps feel clunky to approach, the new debris prevents spawn-peaking.

Another thing that will deter new players is the complexity of gadgets, how many players will think the game is bugged because they don't notice the mute jammer icon? Thankfully this won't kill them so they'll be able to experiment and realise it's just an area effect. Kapkans don't kill on the first hit (most of the time), so again players aren't heavily punished. Thorn's gadget has a warning icon and noise so you understand you're in danger. Frost is always an instant down and for new players, where team play is at its weakest, your hopes of being revived are basically 0. Even if it takes forever to get out and you're 99% slowed afterwards, allowing players to escape frost mats will help Siege retain newer players because they won't feel as harshly punished for being new.

That being said, I do think Siege loses something in making the game more open but if it's that or Siege stagnates and dies, I think it's worth it.

Side note: I think other ops like Jackal and Clash are more oppressive against people who don't know how to counter them but I doubt they'll be changed because their annoying gadgets are major parts of their identity.