Disregarding what the side project even is (only even heard about it after it crashed and burned), i have very much negative confidence regarding taking-on a side project while the main one is yet to get a 1.0 (not EA) release.
The Q&A did not reassure me, as i witnessed failures far more than successes from studios/individuals presenting these rebuttals.
No matter how good the game currently is (and good it is, yet a WIP nonetheless), it was purchased by players as a project to be completed, it is not a matter of legality (indie devs can at any time grab the bag and run without any repercussions), but of trust.
Let's take FTL as an example, it was crowdfunded and delivered, after which they made Advanced edition, which they did not have to, and presented their new game Into The Breach, which was also well received.
While i don't think anyone is demanding free updates post completion (most are probably even willing to buy expansions/DLCs afterwards, Rimworld style), the studio was founded around making this game, as were the purchases, any other objective is unrelated to the original transaction until the game is considered complete by the initial roadmap.
After that? I don't think any meaningful amount of players would have any complaints with what is done with the capital and manpower, as it would be considered fully earned with promises having been delivered, which would further encourage spending toward any new project.