Barrier invocation - possible hidden modifier on gem. Help/Advice wanted.

Barrier Invocation seems to have a hidden modifier limiting the gem level of skills it can use.

lvl 9 barrier invocation, can only trigger lvl4 spell gems inserted.

Im on SSF so cant try a lvl 20 Barrier invocation gem with higher skill gems.

im guessing this is a side effect of the COI,COF,COS Nerfs.

All i wanted to do was get hit all the way through the map and then when i got to a rare/boss unleash a huge flurry of spells. i can do this tbf, but they are lvl 4 spells so not really much point.

ill add that it works with multiple gems and the supports.
Frostbolt - spark - scattershot = will fire both spells with multi proj.
frostbolt - ice nova = will use both spells triggering the nova on the frostbolt.
Unleash will not work unfortunately.

If anybody has had any progress testing/using this meta-skill or has access to a lvl 20 barrier invocation can you test it and see what the maximum lvl gems you can trigger is and get back to me. TY