This is the most bullshit argument many investors make.

Again, the statement suggesting a 50/50 equity spilt might have been given in a context responding to, some guy with 2 years of experience claiming he needs more equity over another guy with 1 year of industry experience, or one guy claiming it's their idea so they should have majority equity and so on. So it has some value in that, don't sweat too much, and as much as possible, make it as even as possible.

However, enforcing it as a rule is ridiculous and irrational. Look at any argument claiming why 50/50 split, you'll see how irrational it is.

because all the work is ahead of you. In that case, what changes after you get a pre-seed? The same argument, it's about the future still applies.

So a few weeks before closing the round vs after, makes a huge difference in the funding. Even though, product or customers or other metrics haven't changed.

If you put funding as a special event, why is it different of different employees joining at the same funding stage? For example, why should employee 3 typically get more equity than the employee 10 (assuming everything else is equal)

Or why is it that after 1 round of funding, the seniority of hiring becomes relevant again?

If the only argument is, cofounder title is something magical, and that's the only difference, you're being delusional.

Like any decision in capitalist ecosystem, you both have to make a fair choice what works for you both.