Question

Joey had been winding up to pitch when Gramps called for a time out.

Answer 1

The tense of the verb ‘had been winding up’ is past perfect continuous. This tense is used to indicate that an action that started in the past continued up until another time in the past. In this case, the tense of the verb indicates that Joey had been winding up to pitch until Gramps called for a time out. At that moment, Joey’s winding up to pitch ended.

Answer 2

The tense of the underlined verb (which is past perfect continuous) tells us that the event took place in the past continuously.
That means that it lasted for some time in the past, but it didn't necessarily finish.