When they made MH bonus stack with phoenix this way, they changed numbers for MH in client files from 1.24 to 0.24. For Timewarp we still see 1.24, so it would either be 1.24*1.2=1.488 (+48%) or they would change it same way as MH a bit later, or some bug would happen.
Can't wait to see how it will turn out
I'm kinda assuming it will still change as you described, since the second effect has not been announced yet, it means its not fully finished yet. But if it does indeed end up as a bug, we (the QA team) are ready for it