These guys are quite busy doing cheap boards all the time. I guess you are allocated customer service time slot of about 1 minute. If any error happens in the process, it's typical they just mechanically write the same reply over and over again, because this only takes literally seconds from any customer service worker, while actually looking at the issue might take minutes from a more experienced person; and they already did it, so what are the chances the result would be any different the next time?
I guess mostly people do the same stupid mistakes over and over again. If I need to guess, the message you got is about having no cutout layer, but having the cutout on the copper layer, which would be typical for many beginners. This diagnosis was definitely in error, but likely, most of the time, it's not.
Apparently, when you asked for a refund, they got an incentive to have a second look and by doing that, found their mistake.
It would help tremendously if they recognized top-10 issues and worked out proper English "error messages" for such cases, using the standard terminology such as "solder mask sliver" instead of "green oil" - so they could copy-paste the proper responses. They have professional website using fairly good language and relevant terminology; they should extend that translation to the most commonly occurring email correspondences.
My 0.02€.