ASA BU SP mechanics question

[NCASAUmp]

There's one section in the manual that has had me baffled for a while now on page 216 (SP BU, 2 ump system):

When there is a play at home plate and the throw to home plate is cut off with a subsequent play at third, they are responsible for the second play in the infield, no matter at what base the play is made.

In every clinic I've been to, I've always been told that BU has 1st and 2nd, and takes the trailing runner to 3rd. That's it. Are these clinics wrong/incomplete? If PU calls a play at HP, then calls the subsequent play at 3B, would they get dinged?

I'd hate to incorporate this into how our local umpires call, as this is not what we've been told, and it would only create confusion between players and our crew. However, if I intend to move up, I want to do it right.

(Jury duty gave me a lot of time to focus on nitpicking my mechanics today.)