Not really true - v0.20 of PicoTorrent [1] was released with BitTorrent v2 support on the same day as libtorrent released support for v2 torrents. I think this predates BiglyBT 2.5 with v2 [2] support with about two weeks.

[1] https://github.com/picotorrent/picotorrent/releases/tag/v0.2...

[2] https://biglybt.tumblr.com/post/629947579144290304/2500-rele...