The thing is that technically the whole drone-specific-mods chapter is optional rules--
These rules provide detailed options for drones and can be used as an optional rules system for adding modifications to them. Players who do not want to use a separate system can use the rules provided in the Building the Perfect Beast chapter (p. 150).
If you do use the optional rules, you can assume that they only apply over the normal vehicle modification rules where they are explicitly stated to be different-- So, the number of mod points, the rules for improving attributes, and the few physical modifications like weapon mounts.
With that in mind, the Chameleon Coating mod just uses 2 of the drone's universal mod slots.
Also, even though they are "optional", some of the drones in Rigger 5.0 are written making use of those rules, and so don't make sense if you don't use them.