HTTP Verbs? You really can't get more basic. At least you could try to wrap your brain around the idea that GET reads and POST writes.
Not using SQL? Okay. You're spending a lot of time and effort hand-rolling your own shitty database.
The combination of things suggests to me they have can't or don't want to deal with with non-trivial mental models. Things like transforming data between layers or figuring out how someone else will read your code.
The next person to work on their stuff is going to have a massive headache figuring out what "made sense" to this person.