wd11: 3.3.2.4 Payload Format Indicator
The last paragraph of this section is the only place in the normative text that we say what a Server must do when sending a property to a V3.1.1 client. We should not in normative text be talking about this at all and it is clearly unenforceable as a MUST.
It does make sense in a more general location to have non-normative text suggesting good practice in this area.