They're mainly doing coding tutorials and day-in-the-life type videos.
Wonder if this could be an issue for the companies (especially if the interview preparation directly talks about how to ace the interview process at a certain company)?
It probably depends on the company and the type of content. I can't see coding tutorials and day-in-the-life type videos causing any problem.
Real example: TechLead is the popular YouTube channel (1m+ subscribers) of an ex-Facebook/ex-Google engineer. His videos skirt the line between parody/satire/hubris (pick your mix).
I got fired from Facebook (for having a YouTube channel) 2019: