4.5% self-report as LGBT. That's an important distinction to make, and I too would be surprised if it's accurate.
[1]: https://news.gallup.com/poll/234863/estimate-lgbt-population...
4.5% is about 1 in 22. 8.2% is 1 in 12. Even accounting for the fact that most LGBT people are as private about their sexuality as straight people are, its often enough that you're likely to encounter LGBT people on a frequent basis.
If the person once identified as LGBT, but doesn't today, is it based on what they "actively" are? Or if you ever once identified as LGBT, for purposes of polling, you remain in that category for life?
sexual fluidity
Based on your context, "sexual preference fluidity" would be the appropriate term.