I would expect that they meant you can't use it on Characters from the DAEMON faction (which makes sense). However, by having both a Faction keyword and normal keyword of DAEMON, they've basically screwed themselves.
giving the lord a godmount only gives the keyword, not the faction keyword.
though it being worth 675 is mostly down to the other eldar anti-tank options being pretty bad
guardians with bright lance: 105pts vyper with single bright lance: 96pts Wasp: 130pts for 2x bright lance Fire Prism: 186 pts for basically just the one gun War Walkers: 101pts for 2 BL
and of course the wave serpent can mount 2 for 172, whcih is why it kicks the FP's ass
since I don't like anything without the FLY keyword, the scorpion and shining spears are the most cost-effective tank hunters I can run besides wave serpents and wasps
or hemlocks, but I prefer using them to hunt elite infantry
to give you the idea:
1x Jetlock 2x Jetseer 1x Vyper /w Bright Lance 15x Windriders with Shuriken Cannons 2x Wasp Assault Walkers (both dual AML) 2x Hemlock Wraithfighters 2x Fireprism 1x Nightspinner 1x Scorpion Type II
I'm going to convert myself some shining spears using the windrider models and some cold one knights, since I don't like the old shining spear models at all