As much as I hate dishonesty, I think it would lead to a very unsatisfactory and confusing situation if McNally applied to catfishing.
In the McNally case, Leveson LJ called for common-sense and said it would be 'depending on the circumstances'... whether gender vitiated consent.
McNally was not charged in relation to any of her 'catfishing' conduct, it was only when things escalated to the point where she was physically wearing a disguise, using a prop to give the appearance of a penis, etc. that applying a broad common-sense approach, the criminal law was invited to step in to address the gender subterfuge.
Catfishing is not illegal. If someone choose to chat with another person online whom they have never met, they cannot know whether the person is male, female, trans, gender fluid (regardless of what the person feels comfortable identifying as). Provided both are consenting to interact and are both adults, it will be for them to be as engage with the relationship as much or as little as they choose. A man who pretended to be a woman to get Imran Khan to do stuff on webcam was not charged. There was also a journalist that did the same to a male politician. Again, no charges.
I think applying the broad-brush common-sense approach that Leveson LJ invites, people generally recognise that people have different online and offline personas. Sometimes in trivial ways (maybe they're carrying a few extra pounds), sometimes less trivial (they're married!). Like cheating and infidelity, it's not a good way to form any relationship - although sadly it happens. There may of course be valid reasons why people may experiment with an online persona if they are suffering with a physical disability or something.
I think if McNally started applying to catfishing it would be the beginning of the end for clarity around consent. It would mean conduct which is a part of daily life would start to flood the criminal justice system. It would mean regular shows like Catfish would suddenly be depicting criminal conduct and have to be taken off air. You would also have a situation where whole sets of people would be perfectly free to lie as much as they want online whilst other sets of people would be criminally prosecuted. So, a 70-year old man would be free to lie and say he was a 30-year old man. But a 19-year old with gender issues could be criminally liable and go to prison, for adopting a female persona but being honest about everything else? A person could lie and say they were a celebrity provided they were the same gender as a celebrity. Does the criminal justice system really want to start wafting through all these types of matters?
I say the law should stay as it is. Allow people the freedom to be as little or as much as themselves as they want online (although educate them on healthy relationships and trust), but if the relationship escalates beyond that: where for example two people are about to engage in penetrative intimacy and one of them is wearing a physical disguise, then the criminal law can decide if it wants to step in at that point!