I could be wrong but the drawings on page 311 and 312 of the 1969 Camaro AIM appear to have been redrawn as they have the different configuration from the 1968 L78.
The A.I.R. pump isn't the subject of those pages - it's just background. All 1968 applications that used the relief valve on the A.I.R. pump (L35, L78, Z28, etc.) show the valve separately as an assembly plant-installed item; in 1969, no relief valve was used, and it's not called out in the 1969 A.I.M. for installation for any application. Those pages were re-drawn (rather than carrying over the illustrations from '68) due to the completely new 1969 accessory drive system which relocated the alternator and A.I.R. pump from their previous 1968 locations.
If you look in L78, sheet A2, under 6T (which is the A.I.R. pump), it says "assembles same as RPO L35; if you go to L35, sheet A2, under 6T, it says "assembles same as production". If you go to UPC 6, sheet A6 (the production A.I.R. pump installation), there's no callout for installation of the relief valve, as none was used in '69 (although the background illustration shows it on the pump). Some component illustrations are more accurate than others - depends which illustrator drew it; their focus was installation and fasteners, not detail appearance of the part.
Observation of hundreds of known-original cars has confirmed that the relief valve wasn't used in 1969 (although it's present on some Service replacement pumps, which cover a number of different applications).