An observation I am curious about

So, as it says, I am a Type 1 Diabetic. Just an observation I've made completely on my own and am simply making this post out of curiosity.

First thing is the pharmacy I went to simply did not have needles I was prescribed in stock. Due to this, the pharmacist asked me if I had thick skin. I thought about it for a second, and since I'm a naturally thin person, I thought well no. But my skin is a little tough around typical injection sites (have been diabetic for 10+ years so only natural). But I was curious, and decided to take a little experiment into my hands (without consulting my GP, although I know you always should).

Anyways, I then thought, "Well, my doctor doesn't even interact with my diabetes...Takes blood pressure and heart rate, and simply takes simple blood tests three months that we don't even really discuss, along with a more detailed test once a year. We don't really discuss it again, I simply learn the information on my own via Google and health resources lying around. So fuck it, let's have the pharmacist just give me advice as they seem to be generally more excited about giving me advice regarding my medication than my actual GP does. Plus, I know my body best."

I decide to take the needles and thought nothing of it, if anything the needles lead to a LOT less bruising which I saw as a huge positive.

But lately, along with my diet getting back into a good place (depressive episodes tend to lead to me eating lots of lazy processed foods), I've been having a lot of lows. Like, even up to 2 per day. I've decreased my long-acting dosage by one unit like I do when eating better. And usually, this alone is enough to stop the constant lows along with being more conscious of little complex carbs and processed foods, I dose lower fast-acting insulin too. I've noticed though, even with all the little little insulin I am taking, I am STILL getting lows.

I am curious, does anyone know if the size of the needles and how deep they go, if this can really make a big difference in how the insulin gets absorbed?

TL;DR Recently went from 6mm to 4mm needles. Seem to be having to take less insulin and getting a lot more lows than I would like. Curious if anyone knows anything about needle sizes and insulin absorption or if this is just simply in my head.

Thanks and I really appreciate it!