There's definitely differing qualities of front projection, but you may also be referring to back projection, which was the lower quality precursor to front projection. Back was low quality process and more limited - it could only be used on a relatively small screen background - and was still unconvincing. Front projection is more complicated and finicky a process. The technique was made possible by the new-at-the-time invention of scotchlite reflective fabric. It produced far higher quality results than back projection and could be used with a very large screen and hence display bigger backgrounds.

couple that with: many of these still shots were likely done with scale models rather than live actors (at about 1/8th scale), so then the front projection background will have an even higher focus/resolution/quality since the image can be projected onto a smaller screen.

https://zen.yandex.ru/media/id/5e4ac3dd5033cf582d873b74/25-samaia-izvestnaia-lunnaia-fotografiia-iz-missii-apollon15-sniata-v-pavilone-metodom-frontproekcii-5f5be64e93cc6c72fff61f06?&

https://zen.yandex.ru/media/id/5e4ac3dd5033cf582d873b74/85-snimal-li-stenli-kubrik-vysadku-na-lunu-postanovka-zadachi-chast-1-617d75f4ab571f2150aa14e3?&

Those are the articles of a Russian cinematographer and film school teacher explaining in detail how all the faked moon photos and films could be done - it's a fantastic series of articles, here's the home page:

https://zen.yandex.ru/id/5e4ac3dd5033cf582d873b74