Quote from Blzut3
While I'm curious on Wub's opinion on the subject, I would say that trying to make the about dialog perfectly accurate is basically impossible. For example Qt5 versions of Doomseeker are technically LGPLv3 or GPLv3 since it's impossible to distribute the combined work otherwise. Similarly Qt4 builds would be LGPLv2.1 or LGPLv3 (not "or later"). And of course this all changes if someone paid for the commercial license for Qt where suddenly the Qt5 version can probably be LGPLv2.1 again.

And as you say technically some one could replace the third party files with ones from wherever which has more implications on the license text. So in my opinion I'd rather just leave it there and overstate.