Yes, but...

The Proceedings of the Royal Society doesn't start until 1800.

I think that's a little misleading, since the Philosophical Transactions started in 1665.

Even then, initially that's published in large, irregular volumes.

The Philosophical Transactions had volume numbers that were quite regular, either annual or biannual, depending on the time period. The Society's website implies that they were printed as volumes, but they were quarterly.
The first 50 years of the Proceedings, before it got that name, had quite irregular volume numbers, but I would be hesitant to draw publishing conclusions from that.

I think that there's some survivorship bias, too. Wikipedia claims that there were 1000 journals in the 1700s, but they didn't survive. So enlightenment might be a better answer than post-enlightenment.

EDIT: the Royal Society's website contains issue numbers, but its organization implies that volumes were published at once.