I was on spiro and a pure estrogen. According to my doctor, the pure estrogen spikes your blood E levels and then quickly tapers off. As your E levels fall, T quickly rises. He said that the restoration of T levels was a constant antagonist towards my transition.
I was at less than 1/5th of my original T value while on spiro and estrogen. It was not enough. He got me on a time release estrogen, estropipate, which I've never heard of another TS taking. He says it lasts 24 hours, so my x2 day dosing gives me plenty of coverage.
If you do not want to transition fully, or transition yet, then it doesn't matter if your T still has some bite. But... if your timetable is 4-5 months, you want to be on the right HRT. If you are older, it may be longer that you can still pull off being a guy.
Estrogen + unblocked T will probably not give you the results you want. If you are young, it will still cause damage to you.