@tagomago I have just got off the chat with them.

Mac OS 10.12 is the latest version they support. I pointed out that as people upgrade their laptops, this means that it's only people who's Macs are older than 7 years old who will be able to use this software.

Then they said to me, "well, why do you want to update your firmware anyway?"

I explained that firmware isn't just about bug fixes, it also provides new features and performance benefits (and gave an example of power saving mode in the latest firmware).

After that he just said it's not supported.

After a bit of to-ing and fro-ing, I managed to get the person to say he would escalate it to the engineers as a feature request. I'm not holding my breath though!