Tyson always buys multiple versions of any clothes he purchases so that he can wear the same thing every day, like a uniform; like armour.
His tendency to pressure stim plays a role in this, but another part is that Tyson has spent years of his life wearing a uniform and separating different parts of his life by the clothes he was wearing.
What he chose to wear around the family manor during Sabbath wasn’t the same clothes that the Delaney family heir would be permitted to wear whilst his tutors were at the manor or whilst representing the family, at home or outside of the manor grounds. One of his few acts of rebellion was wearing his brother’s leather jacket.
Even when Tyson is dressing casually, he will choose specific shirts on days when he’s visiting the Moriarty Mirrors as opposed to sprawling across his settee with Bobby on his chest, both of which are entirely different to the casual clothes he’d pick for days when he intends to run a bunch of errands around London.