That's not "trying to cover it up", that's a link to them adding credits that were missing, which is the main corrective action to get into compliance with the source project's license.

Is that a coverup - eg. are they retroactively rewriting old comments - or are they simply jumping on this and trying to correct the problem?

(Although I would say it isn't a very good-faith effort to address the issue if they don't put back the author attributions they removed).

And if they had instead chosen to remain silent on the origin of the code, how would you have characterized their actions then?