Stonewall might help
TRANSITIONING
The steps a trans person may take to live in the gender with which they identify. Each person’s transition will involve different things. For some this involves medical intervention, such as hormone therapy and surgeries, but not all trans people want or are able to have this.
Transitioning also might involve things such as telling friends and family, dressing differently and changing official documents.
TRANS
An umbrella term to describe people whose gender is not the same as, or does not sit comfortably with, the sex they were assigned at birth.
Trans people may describe themselves using one or more of a wide variety of terms, including (but not limited to) transgender, transsexual, gender-queer (GQ), gender-fluid, non-binary, gender-variant, crossdresser, genderless, agender, nongender, third gender, bi-gender, trans man, trans woman,trans masculine, trans feminine and neutrois.
TRANSGENDER MAN
A term used to describe someone who is assigned female at birth but identifies and lives as a man. This may be shortened to trans man, or FTM, an abbreviation for female-to-male.
TRANSGENDER WOMAN
A term used to describe someone who is assigned male at birth but identifies and lives as a woman. This may be shortened to trans woman, or MTF, an abbreviation for male-to-female.
GENDER REASSIGNMENT
Another way of describing a person’s transition. To undergo gender reassignment usually means to undergo some sort of medical intervention, but it can also mean changing names, pronouns, dressing differently and living in their self-identified gender.
Gender reassignment is a characteristic that is protected by the Equality Act 2010, and it is further interpreted in the Equality Act 2010 approved code of practice. It is a term of much contention and is one that Stonewall's Trans Advisory Group feels should be reviewed.
Seems pretty clear then. Doesn’t mention anything about consistently appearing as the opposite sex. In fact I’m sure that’s part of the GRC process that is objected to.