Trouble is, doing that, keeping both active, with clients on each, introduces throughput problems for the 5ghz devices.
If you’re going to have them both active it’s best to make sure the 2.4 and 5ghz aren’t on overlapping channels. Which is, again, tricky if you’ve got any neighboring SSIDs active too.
Personally, I’d pay a small amount extra for a wired interface into the Rachio. But then I happen to have pulled both AC power and Ethernet CAT5 to where mine is installed.