I am regularly using interactive debugging (-->
bin/client1 debug) and there, I often display acquisition wrappers. From that I can tell you, that they always had the "used for" information; this definitely was not introduced for 5.1.4.
I agree that it seems strange to have an acquisition wrapper display in 5.1.4 when there was none in a previous version (as Zope is on its way to replace acquisition by
__parent__ chaining) -- and I have no explanation for this.