I’ve never had an issue with the whole dual band deal, and nor can I fathom why there should be, when you consider that the Blink equipment can’t even see the 5GHz signal. Some claim to have had this issue, and if you have renamed it to avoid confusion, so be it.
As I mentioned previously, using the same ssid for your extender invariably results in confusion with which device each component of your system decides to talk to. I like your description of seems fiercely loyal, lol, and this was exactly the problem I faced when I deployed an extender. Basically, my camera was as good as sat on top of the extender, and should have had five bars, as was the meter option at that time, but it would not let go of the router, which was a huge distance away and was reading only one bar, in the red.
This is why I said, if you are deploying a separate sync module, and a WiFi extender, to work together, to operate a single distant camera, or a group of cameras, it is much better to rename the ssid of the extender, so you can force that sync module to use only that one. Thereafter, all cameras that you add to that sync module, will use the extender too.
If you don’t do that, and have the same ssid, who knows which one they will pick up on, just as you describe?
If it works, it works, and if you’re happy, so be it. Main thing is you got your very distant camera on the extender. That probably happened because it was so far away it couldn’t even see the router, even if it did have the same ssid.