Trust
What is the difference between OSDP and Wiegand?
OSDP is two-way and carries encryption while its secure channel is on; Wiegand is one-way and unencrypted.
Detail
Being two-way means the panel can tell the reader something: a light, a sound or a status query.
Even where OSDP is installed the secure channel may be off; that is a separate fact and is never assumed.
Source
Source: the protocol table on the compatibility page.