@NBV I concur that the sex scene is more than referencing, but that standing portrait you used is a stretch. That particular pose is exceedingly common, including the hand in the hair. I'm betting I've seen it at least 50 times. I would say that is a better example of referencing at best. The hair is different, including completely different shading and fall. The hand and arm are in a different position. The outfit is completely different, and the only similar shading is on the breasts. Even if he did use this picture as a reference, the changes are major enough that it shouldn't matter. Also, there is no way this particular comparison would earn a takedown beyond maybe the bigger company muscling the indie artist.
I do believe the artist cut corners on the cowgirl scene though, that one is a much better example of going beyond referencing. I will also point out that professional artists copy assets quite frequently. Disney is particular is known for reusing assets. They are their assets, sure, but it's still tracing another person's work. I've always been of the mindset that if you take the artwork and change it enough to fit the current game that I'm not distracted playing it, why does it matter?