It's shite.
It's the inevitable result of adapting the pays to Megaways maths and incorporating a free games bonus. On TSM, as with the original 243-way game, some combinations won't be possible in the maths for 4,5, or 6-reel join-ups. In other words, different reel maps will be in use for different perms of reel joins.
An example in the old game is the fact you can get double bars on reels 1,2 and triples on 3,4,5 but in the 3-reel join-up (last 3 reels) you can only get a maximum of 54-ways of them with 2,1,3x3 and not 108-ways with 2,2,3x3. Or another is the fact you can get diamond and Wild on reels 2-5 when the last 4 join up, but not when you get the max pay of 1080x for 1,1,3x3. So the gimped reels move into a new level here out of necessity.
And yes, calling 10x plus a 'big win' on a Megaways game is a fucking joke, it really is. I thought it was bad enough when IGT did that on Cleopatra when they gimped the original 'quick' version with the pink background to the crappy dark blue one we get spat at us now.