I guess it's just rumors.
"Could possibly be just stupid people in the reviews. I downloaded the game today, popped up in my steam recommended. Played for an hour, finished it, then read the reviews. I did a quick scan, full scan, windows offline scan and 2 sfc /scannow. Nothing, no malware found. In any case I uninstalled the game. The game has been on steam for over a year I think, so im pretty sure steam would have removed it if there was anything wrong.

People call it a miner because of the low fps and big game size (10gb). That is complete nonsence. First of all, no mining software is 10gb, a few mb at most, and second the game is just unoptimized."
This is from a reddit post. There are a lot of reviews claiming it has malware / bitcoin miner but none of them have proof