A question about requirements

[Avri Doria <avri@acm.org>]

Hi,

As I watch discussions in some other groups, and am possibly 
approaching such an issue in my WG, I have started wondering about the 
force of requirements documents published as Informational.

By 2026 definition:

>    An "Informational" specification is published for the general
>    information of the Internet community, and does not represent an
>    Internet community consensus or recommendation.  The Informational
>    designation is intended to provide for the timely publication of a
>    very broad range of responsible informational documents from many
>    sources, subject only to editorial considerations and to 
> verification
>    that there has been adequate coordination with the standards process

yet fill them with words like MUST, MUST NOT, SHOULD etc...

My question is, what force do words like these have in a document that 
is merely informational.

Are IETF 'requirements' only guidelines that MAY or MAY NOT be minded?  
Or have I missed some BCP that defines such force?

thanks

a.