This is a heavy balance slot. The RTP in the buy is in getting a 4×4 or 5×5 out. The game mechanics are weighted towards that happening on a fixed amount of attemps at the bonus buy, so expect a lot of 5-20x features, with the occasional 200-350x when you get a good 3×3.
Ill try and get the actual odds of getting to the 4×4 stage on Monday from Push.