Nonsense. Help to Buy was only launched in 2013, that's only 3yrs ago. The first BTL mortgages were available in the 90s, I believe.
HTB doesn't help (har har) but BTL has had a far, far worse impact.
Let's go back to 2007 and see what's changed. Oh, nothing!
In the last ten years (albeit a short time) I have purchased 7 houses in various parts of the country (sold four of them in that time as well).
The largest increases I saw in both selling and buying without a shadow of a doubt was after HTB. I can only go on experience as a home owner, buyer and seller. If you had been on the housing market around that time buddy you would have witnessed the same.