Is there a particular reason why the backend engineer job requires one to be registered in the Netherlands, which is part of the EU. As far as I know all EU residents have the same equal opportunity to get hired for a job in the EU?
I'm registered in Germany.
> As far as I know all EU residents have the same equal opportunity to get hired for a job in the EU?
Freedom of movement of labour applies to citizens of EU countries, not residents, and nothing about it prevents a company from requiring you to move to their country in order to work for them.
Taxes. You can be employed by a company in another state, but they/you would have to pay taxes according to your country of residence. Even though it is certainly doable, nobody wants the headache of calculating the proper amount of taxes and other contributions for a random country.
The great benefit you are referring to is that you can walk tomorrow in an office in Amsterdam and get hired without needing a visa or anything else, just like a Dutch citizen
I believe that role would require relocation to the Netherlands where we have a large office. The role could still be primarily remote, but NL residence is required.