A questions regarding CIS $compatible string

[jensk]

From CI Plus spev V1.2, appendix G.3:

"A CI Plus host may optionally process the CIS compatibility information. A CI Plus host that processes the
compatibility information and determines that the CICAM is not CI Plus compatible may optionally omit advertising CI
Plus resources or refrain from using specific CI Plus APDUs. Removal of the CI Plus specific APDUs minimises
interoperability issues with CICAMs that are not CI Plus compatible."

This makes perfect sense to me, but then the confusing sentence comes:

"It is mandatory for a CI Plus host to advertise its
CI Plus specific resources to a compatible CICAM irrespective of whether the module is actually a CI Plus CICAM."

What is the difference between a "compatible CICAM" and a "CI Plus CICAM". If the former means a regular (EN50221) CI module does that not contradict the previous sentence that the host "may optionally omit advertising CI Plus resources..." ? Exactly what is the intended behavior from the host side?