Agreed with anjaq. Yeson's work does improve the timbre - in fact I'd go as far as to suggest that those who find the c. 1 month period difficult, might be affected more by the timbre being similar to their old voice than the pitch. This would be expected with swelling, and as it subsides the pitch/timbre reach their new natural state which is much more "resonant" (or perhaps, something to which one can engage the sinus/forehead/skull resonance.)
My own observations are that timbre (not the same thing as resonance), diction, and prosody have the foremost role in a feminine-sounding voice. We emphasize pitch pitch pitch here, which no doubt is important, but if you listen to some female radio DJs, it's common to hear them regularly speak as low as ~100hz and not sound at all masculine because of their innate vocal timbre, combined with how they speak. If anything they sound extremely soothing. But they're also generally able to speak up to ~300hz in their highest peaks of melodic speech, and sound very natural & unforced doing so.
Also concentrating on a program that gives you mechanical readings seems counterproductive to me. Voices are supposed to feel, not measure - to represent our feelings and how we feel. If you want to train new habits into your voice, I'd base them around concentrating on total relaxation and sounding beautiful

Then when you speak in your daily life the use of your voice will be a positive feedback loop with confidence!