Server should not update 'innodb_defragment_fill_factor_n_recs' when wrong system variable provided

Steps:
Followed the below steps to check the invalid system parameters innodb_defragment_fill_factor! and innodb_defragment_fill_factor-. Both are invalid. Server startup ABORTS as expected for innodb_defragment_fill_factor! but not for innodb_defragment_fill_factor-

1. Downloaded the source from https://downloads.mariadb.org/interstitial/mariadb-10.2.4/source/mariadb-10.2.4.tar.gz
2. Compile and Install MariaDB10.2.4 debug build. Use the build script ./BUILD/compile-pentium64-debug-max
3. Change directory to 'mariadb-10.2.4/sql' folder. Run the following commands, change the datadir and log-error parameters path matching to the current installation
4. Execute the following command with invalid server system variable innodb_defragment_fill_factor!

   ./mysqld --innodb_defragment_fill_factor!=29 --datadir=/home/vmatcha/sw/mariadb-10.2.4/data/ --log-error=../data/vmatcha_ubuntu_mysqld_10.2.4-logerror_1.txt &

5. Server startup aborts correctly with the following error about invalid server system variable:

   [ERROR] ./mysqld: unknown variable 'innodb_defragment_fill_factor!=29'

   Attached the log vmatcha_ubuntu_mysqld_10.2.4-logerror_1.txt

6. Execute the following command with a different invalid server system variable innodb_defragment_fill_factor-

   ./mysqld --innodb_defragment_fill_factor-=29 --datadir=/home/vmatcha/sw/mariadb-10.2.4/data/ --log-error=../data/vmatcha_ubuntu_mysqld_10.2.4-logerror_2.txt &

Actual Result:

1. For step 6, Server started successfully with the wrong system variable innodb_defragment_fill_factor-
2. A different server variable innodb_defragment_fill_factor_n_recs got updated with value provided in the wrong command line system variable innodb_defragment_fill_factor-

MariaDB [(none)]> SHOW VARIABLES LIKE 'innodb_defragment_fill_factor%';

+--------------------------------------+----------+

| Variable_name                        | Value    |

+--------------------------------------+----------+

| innodb_defragment_fill_factor        | 0.900000 |

| innodb_defragment_fill_factor_n_recs | 29       |

+--------------------------------------+----------+

2 rows in set (0.00 sec)

MariaDB [(none)]>

Attached the log vmatcha_ubuntu_mysqld_10.2.4-logerror_2.txt

Expected Result:

1. For step 6, Server startup should have aborted with unknown variable error for innodb_defragment_fill_factor-
2. Server should not update a different server variable innodb_defragment_fill_factor_n_recs when wrong server variable innodb_defragment_fill_factor- provided at command line