It sounds like the thing being watched out for is "they clearly didn't do open source things until somebody said that open source looks good to recruiters", and so their recent work is more suspect. Not sure I agree 100%, but the "green dots start when they start job-hunting" pattern is pretty common.
Considering that they don't have a job, and thus have more free time to contribute shouldn't make them look bad. I have a job, I do my job, I go home. Occasionally (like on my birthday) I donate some of my spare time to projects that I care about, and you'll see contributions for a while then I get back to regular stuff which isn't open source. If that looks bad to a potential employer then that's not the kind of employer that I want.
I've been doing volunteer work for the GNU Project since the 1990s. My GitHub profile might not be jam-packed with dots, but I think one would be hard-pressed to seriously insinuate that my few GitHub dots align with the fleeting open source wishes of recruiters... :-)
Though anyone looking only at my GitHub profile might reasonably think so, I guess.
