Hambini is a British engineer who produces great videos evaluating different designs from both a manufacturing and performance standpoint. He evaluates T47 comparing the benefits with engineering difficulty. The T47 "standard" is a larger diameter threaded bottom bracket design which came out in 2015, but it has not been widely adopted. It is like the standard BSA but a bigger diameter.This video explains what they are and how they work. T47 is a larger thread in the frame, 47mm instead of the standard 34.8 mm (1.37 inch) for BSA bottom brackets. They are common on carbon fibre frames.

He lays out several T47 and BSA bottom brackets side by side, and he comments on them. One interesting thing is to remind you that BSA only specifies the BB shell of the frame, the actual spindle diameter can vary, from 16-17mm then 24mm for external cups. Then 30 mm which requires very thin bearings. He introduces 6806 bearings as compared with 6805

I asked ChatGTP about typical axle diameters.

Relevance: The pursuit of different bottom bracket designs conflicts with the value of standardization. In my opinion, the advantages that might be gained by changing the dimensions do not warrant deviating from the standard. Therefore T47 is outside the scope of our "Standard bikes". We stick to BSA thread.

I read the first dozen comments, which gives you an idea it is a discussion aimed at engineering decisions. A discussion which involves both performance and manufacturing difficulty. Eg: I can guess what he would say in contrasting a BMW motorcycle versus Honda. The BMW performance might be better, but is more expensive to manufacture.