Previously we have been marking such changes as major (eg in 1ea47cf), since otherwise npm i for users in old node versions would stop.
Since this already works with node16 and flowzone already was testing this against node 12-18, I would personally wait until we have any other major change to do and get the in together.
Let's also change the title to be in present tense like the rest of the commits, like: Drop support for node < 16

Since this already works with node16 and flowzone already was testing this against node 12-18, I would personally wait until we have any other major change to do and get the in together.

It's ok to mash unrelated PRs together?

We do that only for majors @zoobot b/c customers have raised concerns at some point about doing majors too often making the packages look not mature enough or not well though beforehand.