The explanation of the posting sounds a bit like how my SIL’s job works. He’s technically adjunct faculty at a university. He occasionally teaches seminars on his specialty area to grad students, supervises a few grad students and/or post docs occasionally, but he actually works for (and is paid by) a private institute located on campus.
His private employer pays significantly better (like 2-3x times better) than what he made as a full professor.
He doesn’t feel taken advantage of.