My guess would be the 45 deg taper is likely to not lock as strongly as the 30deg, and might possibly push the gripper balls back under high/interrupted cuts.

Cutwel have the correct studs listed - https://www.cutwel.co.uk/tool-holdin...-stud-standard
I did also find an Indian company last week who had through coolant studs listed at a cheaper price - https://www.toolsengg.com/ps-bt30-45-deg-w-tc.html

Only reason I currently know the spec, is I'm looking for a batch for some new tool holders I've got ordered for my Triac.