"Shipping a binary" is not the same as actually porting the game - porting requires a ton of expensive QA, and no port is better than a bad port because the latter 1) gets bad press for the main version of the game and 2) misleads customers who expect quality from your brand.

Judging by the QC nightmare that game appears to have been, supporting just one installation configuration on an OS with the direct support of the company running that configuration (I wouldn't be surprised if Google had chipped in resources to get the Stadia port through) is a much different level of resource commitment than supporting it for a user base.