As you may remember from anatomy and physiology, is that it takes 28 days for skin cells in your epidermis to reach the outer layer of skin. It takes 14 of those days naturally for the Stratum Corneum to shed in the last stage.
When a person has eczema or psoriasis this 28 days can be reduced drastically to as little as 5 days.
Everyone is different, whether they have a skin disorder or not, as those outer cells can absorb 3 times their weight in water....but if the water content is less than 10% it will crack.
It could be anything from simple dehydration to general skin type or an actual disorder should you have one.
It can be improved by upping water intake, using a proper mitt before a tan (I only use the GLMR works ones), and then after tan moisture such as the crazy angel tan extender or wing smoothing spray is brilliant. You still need to exfoliate after a tan because as I explained, those cells are shedding and that’s where the cracking appearance comes from, because they are literally getting ready to fall off. This is why we preach prep and aftercare..that is why it will look patchy if you don’t exfoliate before and after. It comes off just like the scales of a lizard except not in one piece.
In short, it’s totally normal and you aren’t an alien. We just have varying arrays of normal and we have to accept the limits of our own bodies are not the same as others.