@PrettyDamnCosmic - I don't think any point I made depends on Upton's protected characteristic of gender reassigment. I certainly didn't mention it. Sandie Peggie talked to him "related to the relevant protected characteristic" of his sex - that he is male and not female. This can constitute harassment regardless of whether what she said is true or false, as long as the ET finds it was reasonable under the circumstances for him to have found what she said intimidating, degrading etc. As you say - no need to bring gender reassignment into it, and I didn't.
You might be thinking that it's a defence against harassment to have spoken "the truth" - like it's a defence against libel if what you say is true. As was found in Forstater, you can absolutely harass someone by truthfully and accurately misgendering (mis-sexing) someone. Whether it was harassment depends on circumstance.
@Enough4me - you didn't ask me, but she could win on some aspects of her claim and lose on others. Statistically speaking, a win on all counts is probably unlikely.