the book should cover this
.. this applies generally for any operational document to which a pilot might refer .. unless the specific matter is so "standard" that it comes under standard practice considerations.
The problem is: while those in the know may be able to divine what was intended, but left out, it is totally unreasonable (not to mention potentially dangerous) to presume that all readers will have the deeper knowledge to "read between the lines" to determine how to handle omitted data.
If a manual does not have guidance to cover all eventualities in its use (other than for standard practice considerations) then the fault is with the book and the matter ought to be referred to the document sponsor for review and correction.
Many of us could rattle off a long list of horrifying workarounds developed in ignorance by well-intended folk in the face of badly constructed documents ....
Dassault seems to choose Vr = V2 for the Falcon 50, at all times
Not done much on the Falcons and not for a long time so I shan't try to dredge the memory ...
A couple of points
(a) the Design Standards (FAR 25 and the like) give the starting point .. in a specific certification, though, numerous minor workarounds and changes may be negotiated between the Authority and the applicant. If we wish to migrate a requirement from the Standard to a specific aircraft, then the information in the TCDS also must be consulted .. the bulk of changes are noted in the TCDS for the Type. Add to this a host of minor agreements which don't make the TCDS and it becomes very difficult to pontificate on the specific without access to the certification records.
(b) the Design Standards are an evolving beast and, generally, don't apply retrospectively. As for (a), it is a brave person who tries to migrate the current Standard's requirement to a specific Type without checking the TCDS first .. usually it is necessary to go to a superseded version of the Standard to get the starting story ...