Now. What happened was, SSG introduced an Experimental tumble which meant you could trigger it while running (previously you could only do it while stood still). But you tumble faster than you run, and so the experimental tumble they brought in just meant that everyone was fast now, you dont run you tumble, and you moved waaaaay faster (I miss it to be fair because it was fast and fun
) And so to counter it, they introduced charges to it, so the tumble is still more useful than it once was as you can do it mid sprint, but you can only do it twice to begin with and have to wait 8 seconds for a charge to recuperate. The game tracks individual charges correctly and so you could in theory do 1 charge every 4 seconds if you time it right, you get the idea. You can also get more Tumble charges from multiple sources I believe but I havent looked into that.
So yes it is odd, but. It is the middle ground SSG found so that we can keep the more recent version of tumble without exploiting it.