Is this note in the Standard still accurate?

From the Z-spec 1.1:

The opcodes EXT:5 to EXT:8 were very likely in Infocom’s own Version 5 specification (documentary records of which are lost): they seem to have been partially implemented in existing Infocom interpreters, but do not occur in any existing Version 5 story file. They are here left unspecified.

Emphasis mine. Is this still true? I thought Infocom’s specifications were recovered and published around the same time as the source code.

(And if so, do we know what those four opcodes did?)

(From a bit of poking, my best guess is that they were graphics opcodes for displaying images, which never actually got used until Z6/YZIP.)

The “zip/xzip/yzip” document (dated 1989) lists them but doesn’t (at a quick glance) say which version of the machine they officially went in at.

Looking at the specifications in, I see them mentioned in both the xzip and yzip specs, but not in the zip and ezip ones.