Given everything I know about feature extraction/embedding, my armchair answer would be a resounding no... Given enough similar content the water mark would get rounded of as what it is -- noise.
Also, The fact that a service which in theory would have a high demand, offers 0 explanation or justification for their technique is highly suspect.
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The only way a watermark would be even remotely effective as a deterrent would be if everyone agreed on a fixed mark; this mark could be automatically detected (this a silly way of doing things), or if it was incorporated into the model would create a bubble of locality due to feature alignment (poising the well)
Neither of these are practical or reasonable solutions like: robots.txt, EXIF metadata, and digital signing - combined with regulations allowing for legal recourse
TL;DR - DRM of publicly available data is not a "winnable" fight
