Hmm, these are 38mm tyres and the sealant volume isn't sufficient for the stem to dip into the sealant. I can see that you might get wet sealant drying in the stem if it's at the top of the wheel though. But why 45 deg?
It means not only does the sealant drain from the valve back into the tyre, but it also avoids it being sucked from the pool at the bottom of the tyre into the valve when air is released. At least that's why I do it that way.
Hmm, these are 38mm tyres and the sealant volume isn't sufficient for the stem to dip into the sealant. I can see that you might get wet sealant drying in the stem if it's at the top of the wheel though. But why 45 deg?