Prima Facie, it would seem that the stock cam [H1000] was used from start to finish of 1200 production. It is listed only as 'camshaft' indicating a single part. The book shows the tapered plug at the back as being included but the dowel for the sprocket at the front as separate.

The H7000 part is described a being an 'assy- camshaft' which would indicate something made up of several parts assembled together. [possibly with the dowel]
Introduced in July 1972, it supercedes the H2300 assy- camshaft [the GX cam] which is not listed in your parts list at all & it should be since the new one is not interchangeable with it either backwards or forwards, yet supercedes it.
My book shows the GX cam [H2300] as being used throughout the 1200 GX production run, unchanged.

Unless something more comes to light, I will agree that it's probably an uncorrected error in the US book.

For those not familiar with the parts books,
the heading 'ICA' means 'interchangeable' & the sub headings 'N' & 'F' are 'new' & 'former' with the indicator 'N' obviously meaning 'No'

EDIT
My B120 [Ute] microfiche shows the H1000 cam was replaced in November 1975 with the H5000 cam.

If this is correct it would suggest that the earlier [front distributor] 1200 engine remained in use, in B120's untill October 1975 which might go some way towards explaining why South African 1200s were still using the 1200 engine in 1975 production. [1200GXman]