The problem with the 1646 date is this:1646 is the date I am most comfortable pointing to (in relation to documentation). 1717 (disputed) is only the date of the 1st Grand lodge. IMO, if a person considers our current system as its beginning... then the date would be 1717. If a person considers speculative Masonry, the date is 1646. There are earlier dates with documents which suggest much earlier, but again, things tend to get very murky with leaps of faith. As always, just like everyone else here, Just my opinion.
You assume that a man joining an operative lodge and who has no interest in working upon stone and learning the hands on aspects of the trade is a speculative freemason rather than the more realistic explanation of being merely just another member of a stonecraft lodge who simply wants the social and business benefits of membership in a stonecraft lodge.
That requires a leap of faith that far too many Freemasons willingly make. Just because someone joined these stonecraft lodges doesn't automatically make them speculatives in an operative world. There were many advantages of membership that had nothing to do with speculative assumptions.
Occum's Razor: The simplest explanation is usually the correct.