There is a difference between
- Parallel octaves between two independent melodic lines
- Octave doubling of a line as a method of strengthening the orchestration
The first of these is the "bad" version of parallel octaves that we seek to avoid in contrapuntal writing, largely because two independent voices briefly merge into one and lose their independence. The latter type happens, quite frankly, all the time.
Here is a recording of the piece, and a score can be found on page 21 (25 of the PDF) here. I don't see or here any problematic parallel octaves here, but you're welcome to point to a more specific part of the score if you like!
I don't have any firm evidence, but a Froberger piece on page 64 (84 of the PDF) here is vaguely similar (same key, similar opening arpeggiation) to the Couperin; maybe that's a start?