It's been so long since I've used the old Apple keyboard that I wasn't sure what did and did not repeat back in 2015 and before! I thought some characters, besides symbols, used to repeat. Like maybe "x". But maybe not. I know that space repeated, but that is trickier then space on the TB does more than one thing!
Anyway, I have two old Apple keyboards. Last time I got them out, just to have at least one paired in case I needed it, I had trouble. One wouldn't pair at all - seemed to not even turn on. At least I never saw a light come on.
The other did work so a little while ago I tried to use it to check the repeat issue. Pressed the power button and, I think, saw the LED flash twice. It definitely came on. But, unfortunately, the LED doesn't stay on. So that makes it harder to tell if you have power or not when things are not working. And it did NOT work even though a few weeks ago it did.
But since the LED doesn't stay on, I didn't know if it just wasn't connecting to my iMac or it lost power (batteries were only a couple weeks old too and hardly used in that time).
Looking at BT prefs, it wasn't paired up. Pressing or holding the power button didn't light it up again. Tried removing the device from my BT list. Nothing worked. Opened up the battery compartment and closed it again. Nothing. Finally put in new batteries - still got nothing, but after putting in the original let again, I got the pairing numbers.
But I still don't know if I have a flaky electrical connection in the keyboard or some other problem (or multiple problems!).
I guess, from time to time, I'll pick it up and turn it back on, just to see if the LED fails to briefly come on again when turning on or off the keyboard.
Anyway, the apple keyboard essentially had the same repeats as the TB - except it would repeat space and the TB does not.