Gtid Position difference between MariaDB version

Hi,
We got an issue in our project during the MariaDB upgrade from 10.1.38 to 10.1.41 version and 10.2.18 to 10.2.27 in my project for different branches, which caused problem during the start of Database Replication. MDEV-20637

On analyzing, I could see a weird behavior during MariaDB Installation with the below my.cnf.

I tried to reproduce the scenario as simple as possible by a shell script mariaTest.sh with the below simplified my.cnf file.

[mysqld]
server-id=1
log-bin=binary-log.
binlog-ignore-db=mysql
binlog-ignore-db=performance_schema

from where I could see the difference in the output of gtid_positions in v10.2.18 where first 3 positions are null while in v10.2.27 it has 0-1-1.

As part of my analysis, I could see the above difference only after adding "log-bin=binary-log." properties in my cnf file. while without the property I could not see the above difference.
Confused about the behavior after adding this property.

Can you please clarify the above behavior? Why the position get affected after adding "log-bin" ?
Or Is there any mistake I am doing in the my.cnf file?