I don’t think this is allowed. Comments welcome.
1… Feed to sub-panel passing through distribution area.
2… Double tap on main lug.
If it is being fed by the top breaker and nothing else comes of the breaker then looks OK to me I am concerned with all the red and black wires coming from the lugs at the top This is Double ,double,double ,taps big, time not allowed
You are correct, it is not allowed, assuming your diagram is correct.
The double/triple taps are also wrong.