After some Tests I was VERY surprised, that Lanczos resizes significant sharper than all other resample algorithms (test with different indoor and outdoor fotos, no graphics or similar).
I'm not sure if your "Size Maximum" uses this Algorithm, but it would be nice, since most people will use this feature for fotos, not for graphics.
Suggestion: "[] Size Maximum [Algorithm]" to select the desired algorithm
or a more simple Suggestion: Simply write down the algorithm currently used: "[] Size Maximum (Lanczos)" ... and change to Lanczos

Thanks for all updates!
Bruno