Bind zone file not updated while record is OK when doing an nslookup

I've set up a zone as a master with allow-updates from a windows DHCP Server (authorized on IP only) when I do a release/renew on a Windows workstation, I can see the PTR record updated/created successfully in a bind in the zone.

if I do a :

nslookup IP MYDNSSRVIP

I can see the PTR updated/created successfully.

however, when looking at the zone file (e.g., 1.1.1.in-addr.arpa), the zone file is not updated immediately (if I open it, I can't see the record yet)

does the "datafile" itself take some time to be refreshed? (as I can see the record successfully created when doing a lookup) how is that possible?

or does it mean that something is wrong somewhere in my config and the lookup comes from somewhere else (e.g., a delegation, etc.)