If you’ve got a construction loan lined up with an institutional lender for your construction project, then you will automatically be qualified for the take out mortgage, assuming you are a self builder that will occupy the building at the end of the construction project.
The same will not be true necessarily if you have a private construction loan from a private lending source.
Privates don’t always require you to have a take out mortgage at the beginning of the project and can allow you to wait to the end to get one in place.
But just because you can wait, its probably better that you don’t in the current market and get everything arranged quickly to protect against rate increases.