I believe it's pretty common in the programming language literature to refer to `yield` a delimited control operator. E.g., see http://parametricity.net/dropbox/yield.subc.pdf, which says "yield...turns out to be a delimited control operator of comparable expressive power to shift/reset". A good hint that you're dealing with a control statement/operator is if it's responsible for transferring execution to another place in the code: e.g., `if`, `for`, `while`, `throw`, etc.

Saying that "yield is not about control flow, it's about lazy sequences" seems like saying "functions are not about control flow, they are about producing values".