The Location and Speed characteristics in section 3.137 of the Bluetooth GATT Specification Supplement document defines the Heading field (Version Date: 2024-02-21)
It is specified as a uint16 with a unit multiplier of 10^-7 degrees.
That seems obviously incorrect. A uint16 has a maximum value of 65535. When multiplied with 10^-7 it gives a maximum of 0.0065535 degrees.
I have found some implementation that uses 10^-2 as multiplier instead. Does anybody know whether that is what it should be?
How do I submit an errata on the specification, if I am not a Bluetooth SIG member?
This is almost certainly an error as you suggest. In the Navigation characteristic, Heading is defined as d=-2, just as you've seen. (Errors like this aren't incredibly common, but they certainly exist. I've run into clearly erroneous values before.)
You can fill out an erratum as a Jira. But I don't believe you can access it without being part of a member company. (Adopter membership is free, but it's really only for companies.)