Interesting fact, I didn't know that.
What you or I know does not matter unfortunately; it's what the IO knows that matters.
When I did the OA to O conversion last year, the low rank document checking lassie at the Hua Hin IO told me I could not use my BKK time deposit account (used ONLY for immigration) could be used. I had to establish a new one and USE NEW funds to top it up!!!!!!
Of course she was wrong but it did start the bank trips over the next two days to prove I had funds there for several years, and all had been funded by FTT deposits.
Thanks.