That's exactly how a training should be stopped always - on a good note without pushing

I always give a bigger treat at the end of the session or when I have to stop, still somehow he doesn't abuse that.
Would you believe me a GCC and Quaker hobby breeder told me the same? He really likes Quakers much much more because they're less nippy AND less noisy/prone to shouting? In Hungarian Quakers are literally called "friend parrots" (barát papagáj)
And thank you for clarifying the mutations - those are the only two common mutations I couldn't figure out entirely.