| Whatever bubbles collect in the radiator should get cycled
| out to the reservoir each time the engine warms up.

Only if cap ( like my Toyo cap ) puts too little pressure on coolant
, & coolant gets hot enough for bubbles' pressure to exceed cap's.
Even then, not all bubbles will escape ; when bubbles escape,
remaining bubbles' pressure will drop til < cap's, then no more
bubble will escape.