If you specify an EXPLAIN modifier with a request in 2PC session mode, and that request is followed by a 2PC function, then the SQL portion of the request is explained, but the 2PC function is not.
For example, if the following multistatement request were submitted, the INSERT and SELECT would be explained; the VOTE would not be explained. The VOTE is, however, sent to the AMPs:
EXPLAIN INSERT tab1(1,2) ;SELECT * FROM tab1 ;VOTE
VOTE is specified by the system administrator, not by users submitting requests in 2PC mode.