7985 is not supported by IPMA and the information provided in the links
(for IPMA documentation) is correct.
There was a confusion between phone and IPMA teams because of which you
see a contradiction between their docs.
The reason that IPMA does not support these phones is - not enough lines
to configure phones for Manager/Assistant. Though there are ways to have more lines in the model but User experience as a whole gets affected,
due to which IPMA does not has any immediate plan to provide support for
these phones.