No one attacks more from bottom than Mousasi, period. He's won two Dream tournaments off his back.
The King Mo fight was one of the worst title fights I have ever seen in any half way decent organization or better. Where was he off his back there? Sloppy Mo laid on top of him as Mousasi did throw some elbows. But nothing that great to beat a good fighter doing that.
Other than an upkick that happened to land on Jacre, Mousasi hasn't done things off his back vs. anyone worth a damn. Tex is very strong, has a very "heavy" top control, is a devastating puncher from top, and is very well versed in BJJ and grappling overall. Not saying Mousasi doesn't have tricks from his back, but Tex isn't the cans he showed off against in Dream.