Hello Aphaea,
I am sorry you have that experience, but thanks for posting it. I dont like it if the forum gives the impression of being one-sided. I have a few thoughts on this and a few questions, maybe it can help.
Ok, so first a more general question - those two women you met in Korea - they also had VFS with Dr Kim, but were a year post op when you arrived there for the surgery? Did you meet them by chance, were they at the clinic for a revision, or what was the circumstances of your meeting? Have you been scared by their experiences, given you just were about to have that surgery? The one who had a feminine voice from training before the surgery - what was her expecience - did she have more trouble having it post op or was it easier for her to use it?
Next question: Have you checked your lowest possible not pre and post op. Does your voice break away when you use it now at 140 Hz? the background is this: My lowest note has increased from 85 Hz to about 120 Hz - I can speak at 140 Hz or even 130 Hz , but whenever I go low at the end of the sentences then, the voice just fails because it cannot go lower. If this is what is happening to you, you are using your voice at the very lowest end of its range.
Another question: What about your upper range, your transition to the head voice and your head voice in general? The Yeson exercises should train that transition zone - starting at a comfortable pitch and then go up to the G above th emiddle C which clearly is into the head voice zone. Was that easy for you, did you feel te voice break there, was it an issue for you? What was a comfortable pitch to start the Yeson exercises with (the mmmmiiiii one for example, or the lip trill)?
Is it easier to use higher pitches now for you? I found it is not so much that the pitch is forced up by the surgery so much as that it allows or enables to use higher pitches comfortably. Women use low pitches as well, but for a womans voice it is easier to use high pitches as well, so it has a bigger vocal range when speaking and this gives a higher average pitch. It can still be as low as 130 or 140 Hz in some sylabils, but then it shoots up to 260 or even in the head voice and then goes down to 200 again... Thats ok, as long as you dont get locked in at the very low end of it.
Ok, thats a truckload of questions so far, maybe you can answer a few of them?
My general advice without knowing the answers would be to go and see a speech therapist - ideally a gender specialist, but it can also be a regular speech therapist who just focusses on you using your voice in the range that is optimal and who knows how to train for a more vivid voice (you can , if you like, post pre and post op recordings here so we can maybe hear what issues might be present).
I think the Yeson instructions and exercises are not really enough. They are a bare minimum you get because they cannot give you regular checkups or prescribe voice therapy in Seoul

- Dr Kim told me I should start with my voice rehab therapy after 8 weeks and I get a prescription by my local ENT for it, she also does post op endoscopic video checkups and I send them in to Dr Kim. Dr Kim also takes voice recordings via email and can analyze them for you and tell you what issues are possibly present.