Who gives them this “advice”? Utterly clueless.
for a start, direct discrimination is “less favourable treatment” than someone without a particular protected characteristic would receive. It’s not clear at all that having a single room as opposed to a ward is “less favourable treatment”.
secondly, a TW with no GRC is still legally male. So their comparator is another man. Hence no discrimination. Notwithstanding the comment above.
thirdly, even where there is a GRC single sex spaces can still be used under exemptions in the Equality Act.