Will is not per se the specification of a requirement but is used to indicate a statement of fact. Will statements are not subject to verification. For example: if I want to tell you something about another system I will use “will”. “The XYZ system will have the timing as defined in an ICD 1234.” Or if I am giving a description of something that exists today, I will use “will”. “This report will contain this data…” In a statement of work (SOW) or task order for a vendor or supplier, I use will to communicate something I will do for or provide to the vendor or supplier.
Also see: RFC2119 - Key words for use in RFCs to Indicate Requirement Levels .
Source: https://reqexperts.com/2012/10/09/using-the-correct-terms-shall-will-should/