It’s interesting to note that it’s the Home Office which is responsible for DBS, not Department for Education.
That would seem to suggest that the DBS was originally envisaged as protecting vulnerable individuals from acts that reach the level of criminality (sexual assault, voyeurism, physical assault) and not envisaged as covering philosophical objections to / well-being concerns about the impact of campaigning by external lobby groups with a background in seeking to confuse children about reproductive biology.
However I guess there will be relevant arguments relating to DBS policies on safeguarding in non-education settings that could be relied on by DBS to support their approach.
I’d guess that the DBS will go with a black and white “there was a policy and you refused to follow it” defence. Which may well win the day. Perhaps the complainant will argue that if it’s about protecting young people from harm, the question of whether the lobby groups are causing the most harm, or those concerned adults seeking to moderate the impact of those lobby groups’ endeavours is a question on which DBS have ‘picked a side’ without appropriate prior consideration and that this question is a live issue as evidenced by the guidance. Also that there is no evidence of actual harm arising from “misgendering” other than those lobby groups’ self-interested and hyperbolic claims. Reading the article, the complainant’s key argument is that the penalty was disproportionate.
It will be very interesting to see how this pans out.