I think 25.M.1.f.ii covers this:

f. A reserve pilot who departs his domicile to operate a domestic duty period shall be scheduled for release to a legal rest period not later than 4 hours after the end of his RP. This paragraph shall not apply:

i. to a pilot who is released for a legal rest period prior to the showtime of his reserve assignment; or

ii. if the reserve pilot is assigned to a duty period consisting exclusively of deadhead.