Doing some research into what the 6.7 U3 patching would look like for a client, I was trying to be a good admin and look through the compatibility matrix and see if anything jumped out. Well it did..
Basically, unless you have already updated your Horizon environment since July, which is when Horizon 7.9 came out, you should probably wait on 6.7 U3 until your Horizon environment can be upgraded.
With Horizon upgrades generally being more involved than core vSphere, often people are patching and updating vSphere on a much quicker cycle than Horizon. In this case though, it could cause some compatibility issues if you aren’t careful.
In case anyone wants them here are the release notes for both 6.7u3 and Horizon 7.9