Both upgraded to macOS Mojave 10.14.6 18G103 - It took me a while to notice on the MBP because I use it as a desktop with a wireless keyboard and a dust cover over the built-in keyboard, but I upgraded the MBA, noticed this on the first restart, and then came to see that the MBP has the same issue. Reset PRAM/NVRAM & SMC on the MBA, no change.
Any idea whether it's a known issue or what else I can try?