Without using the 1hz url parameter, I could not tune arbitrarily between the 10 hz increments on the K1VL receiver. It would round and tune to the nearest 10 Hz.
Ah HAH! It's not just me imagining things.
... After having fun doing it by ear, I went to SAM mode and did indeed notice the audio panel's sync offset display respond to those 1 Hz steps (or not, if I didn't have 1 Hz tuning enabled).
Ok, well I was right for a little while anyway.
That sync offset is a pretty slick way to compare receivers, if you tune them both to the same station! After picking and poking around on several receivers, checking then against WWV, I can say that most are within a couple of Hz and some are dead nuts on frequency - within a few tenths of a Hertz, plus or minus some QSB effects.
If they are GPS locked with acq[uisition] of enough satellites (hopefully 4 or more), I would hope so.
I have encountered a few non-locked (I assume) in the southern hemisphere that are ~100 Hz off frequency at 10 MHz - which might not be a big problem in some contexts - but can be misleading in others like FT8, where the TX bandwidth is only ~50 Hz and accuracy down to <10 Hertz is kind of important.