If you look closely at rate in this little gif you'll notice how the target rate jumps from 196 to 96 towards the end but also jumps from 846 to 946 at one point while out of the water. I've been exploiting this to cool down faster, but of course, I'd like it to be fixed if it is indeed deemed a bug.

I'm playing the Forever Stranded modpack which is on MC 1.10.2 with (old) version 1.1.1 - so it is possible this is fixed in the newer versions for 1.12.x.

Thanks @Adubbz. when I saw the version difference I wasn't sure whether this was still a thing, but better to report it than not to.

Rate was changed completely in newer versions, so this is not really possible anymore.