I wouldnt untie it yet, because Like I said, its only what Ive read.
Heres a thread.
http://boards.cannabis.com/advanced-techniques/145561-can-i-lst-during-flowering.html
But anyway, like said in that article^ Whats the point of LST during flower? At that point youre no longer trying to add more budsites because youre already in flower, its mainly to get light to the lower part of the canopy no?
After a lot of reading, people say it can be done during flowering. Theres so much conflicting info on this stuff man, its hard to pick what to believe in haha.
I hope you find what you are looking for. Good luck!