I think people are just asserting what is and isn't possible without stopping to consider that they could be wrong. Whether the original photo is or isn't a composite, I don't know. Even as an amateur photographer, I do know that a non composite photo is possible that will look very close to the original.
Every single photo you linked to, the clouds are visible over the moon. It can be subtle, sure, since you end up with very wispy clouds that have a similar color to the moon, but the clouds are still clearly affecting the appearance of the moon.
The bpotu photo is the one that looks the most like the moon is over clouds, but I think that's just because the right side of the moon is so bright and the clouds there are so thin. But even there it does appear to be very slight discoloration caused by the clouds intersecting the moon.
https://www.flickr.com/photos/rinathompsonphotography/840700...
https://www.flickr.com/photos/backyardastronomyguy/338080684...
https://www.flickr.com/photos/bpotu/15309316569/
https://www.flickr.com/photos/jeffmaack/14693912932/
https://www.flickr.com/photos/encouragement/14442442441/
I think people are just asserting what is and isn't possible without stopping to consider that they could be wrong. Whether the original photo is or isn't a composite, I don't know. Even as an amateur photographer, I do know that a non composite photo is possible that will look very close to the original.