At a micro, it is not uncommon as some of the girls will rush the first shot with an over-the-top oral effort; main reasons are a) she gets tipped for a second round; or b) she can easily coast for the next 45 min.
For a RMT/semi legit; I do not believe that I have ever done MSOG in a normal session. I enjoy my massage too much to rush things. Based on a discussion with one of you here, I tried once to ask my regular to reverse things. We did the nasty bits first the massage later. My friend liked it with his regular because timing is never an issue, there is no rush on the fun bits, he could take his time and get a massage with whatever time is left. I tried it and did not like that arrangement, I felt that there was no build-up to the session and my regular did not like it either because it ruined her routine and ability to build up to a great finish.
I think reversing the order may make sense if you routinely book short sessions, say 30 min. OR (why I mentioned it here) if you are gunning for a second shot at the end. I think my mentality is different as when I see a RMT, it is massage first, happiness second. If I wanted happiness first, I go to a micro.