Here is an example from Nethys: Winter Witch Cold Sister
Even if you modified the extension to work with this format, it would still be wrong for FGU however. While you don't see the problem with the normal HP option (as it takes the HP from the hit points line), if a GM selects "max HP" or "random HP" in the options, the line with the 9HD will cause a math problem (as FGU will add that 9 to the HP).
9HD; 5d8+4d10+59 -> Max = 139 but will show as 148 due to the extraneous 9HD in the line.
I know that I edited these cases out of all the content I developed. Hopefully others did too and this is just a rare case of it left in.
It's probably just better for the OP to report the issue as a bug for the DLC product that has the issue or to just edit out the extraneous information as you originally suggested.