Hey

There are a few effects on Kisame's barrier.

It does deal [ Interruption ] However, it also prevents both players from overall casting.

Interruption has a few merits to its effect.

Priority goes to Barrier Interruptions (Due to the casting prevention) over Mystery Interruptions.

Immunity to interruption only applies to skills that are targeted.

However, in this case, it's an overall barrier which will trump immunity

Hopefully, that helps!