I see what you mean.
If a company is expecting people to do their training based on side projects on their personal time, they are crazy. And that would be a red flag on the company. That's a big no-no.
For me, asking about side projects is more of giving a chance for the candidate to shine. I mentioned it on another comment, people tend to be more talkative and knowledgeable about things that they are passionate about. In that sense, they could get brownie points by talking about one.
Also side projects are not only for training (because not all of them are related to coding/work), as Daniel mentions on his tweet, those projects (development, craft, hobby) build up character, and teach lessons that cannot be learned in a classroom... things that can normally be seen on how people talk about them.
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