Plenty of women have purposefully deceived men into conceiving, I don't think I've ever heard it classified as rape.
This again FFS. Women cannot rape because the law defines rape as a crime committed using a penis. Sexual Offences Act 2003, section 1, look it up yourself because I am sick of posting the link. You might argue that a woman purposefully deceiving a man into fatherhood could be classed as sexual assault, but you cannot argue for that to be rape.
The other aspect of this is that no man ever had a baby or had to have an abortion, both physical consequences to the body with associated risks and harms, after unprotected sex. When a man "stealths" a woman, he puts her at risk of physical harm without her consent. Physical harm is not the same as financial liability for a child.
If you agree to sex because he says he's single but it turns out he's married, is it then rape because you wouldnt have consented if youd known?
Here we are back in the interesting territory of trying to decide if and how to legislate sexual ethics. My view on where to draw the line is that you have sex with a person's body, not their marriage certificate and not their paycheck or their job. So if someone lies about an aspect of their body, e.g. their birth sex, their STI status, or their contraceptive use, I'd consider that as possibly criminal sexual offending although you'd have the difficulty of proving intent. If they catfish you or are a cheater using you as their "bit on the side", that's shitty behaviour but should not be criminal.