British capital ships had flash precautions before Jutland

Did the British 12-inch and 13.5-inch capital ships actually have flash protections for passing charges?

Yes. All had protections, although the arrangements and levels of protection differed.

The older 12-inch and 13.5-inch ships had protective arrangements for handling charges. Their levels of protection differed, but all had precautions. The existence of safeguards is separate from the earlier discussion of crews defeating them to move ammunition faster.