Currently (since ZBX-4793) displayhints are unconditionally applied, the "unchanged" preprocessing does not affect the displayhint change (documentation could be improved as per ZBX-25661).

In some cases, skipping displayhint is needed - for example, HOST-RESOURCES-MIB:hrSystemDate.0 returns DateAndTime, which is hex like 07 E8 0C 02 07 18 18 00 2B 00 00. This can be reasonably parsed into unixtime.
With displayhint it is transformed into something like 2024-12-2,7:24:33.0,+0:0 which is much less convenient to parse, if only because of the single-digit month/date most of the time.

Disabling displayhint processing per item or as a preprocessing mechanism would be great.