Possibly because some ATC units will reply 'Cleared to descend with the procedure, report base turn complete'. The inconsistency of which leads to such things.
At a military you get RT such as 'Cleared to descend with the procedure report steady inbound' or similar.
Talking of which as a quick aside...but who in the military came up with 'Cockpit checks, report complete' WTF? Whats wrong with 'Report cockpit checks complete' which firstly flows better and secondly fits the RT patten correctly i.e. 'REPORT' followed by the what/where and the conditions rather than some interspersed phrasing.
But as I say...its these differences between various units regarding their wording that tends to leave pilots potentially confused.