A trans woman's biology is quite different from cis men, yes, but it's also not exactly similar to cis women either.

Even after a full transition, trans people often are in a sort of intermediate state in terms of immune, cardiovascular, and metabolic systems. They're not exactly like their AGAB nor their new sex identity either.

There's even organ carry over as well. Trans women are the only category of women that can still be at risk for prostate cancer, and trans men are the only category of men that can still be at risk for skenes gland cancer.

The most honest description is to say that they are in an intermediate sex.

Even more so, neuroendocrinology is not fully shifted even after transition. The HPG axis in trans women lack ovarian effects, and in trans men they lack testicular effects.