Ive had him for about a year now and ive noticed that i have to feed the thawed mouse at a certain angle in order for the ball python to strike properly.
if i just leave it in the cardboard box or dangle the mouse by the tail itll strike the neck and basically try and swallow the mouse whole horizontally
should i be concerned? will it ever learn?

You shouldnt be too worried. my snake eats frozen too and is completely uninterested in them unless I dangle it by the tail too. Which causes her to eat the mouse backwards for the last 3 times lol
They usually learn to search for the head on their own but as long as its eating and pooping normally you shouldnt be too concerned

no need to be concerned. If you always been feeding him prekilled he doesnt really have his instincts to go for the neck and wrap. He will eventually learn a good thing to do is mimic the mouse being alive by holding on the tail and pulling while hes biting it usually gets them going and they will start to constrict.

Your snakes aim is true. Though hes your domestic pet you cant breed out eons of instinct.

To avoid injury the snake strikes fast and hard holds and wraps. He wants to disable the biting end of his food as quickly as possible. He just doesnt understand F/Ted and it cant hurt him.

Even snakes that take prey passively from tongs will exhibit this same feeding response. They bite and wait.

A safe strike zone for your snake is the neck of the prey disabling its ability to bite in defense.

What you see as trying to swallow it sideways is most likely his further care to avoid being bit by his meal and moving it with his jaws to position it instead of letting go and swallowing from the head. He will mouth the prey around and into position before swallowing it by the head.

Some snakes take longer to approach the biting end of their prey the nose. They seem to need even more time to feel secure its dead and cant hurt them before they release or swallow.

I see this behavior more in younger snakes but some adults will continue this caution.

Its nothing to be concerned about. His instinct for survival is just a tad stronger and hes more cautious about eating his meal.

Enjoy your pet.