Owner Group Write Permision to an HDFS path

I have run the following test case several times and got the same result.
Context:
1. My HDP cluster uses the simple mode to determine user identity. Kerberos is not enabled.
2. Below is the permission on hdfs folder /data/test

drwxrwxr-x - hdfs hadoop 0 2020-02-07 13:33 /data/test

So hdfs (the super user) is the owner and hadoop is the owner group. Both the owner user and owner group has write permission on the /data/test folder.

Steps:

On an edge node, I used ID command to confirm that the logged on user "testuser" is in hadoop group.

$ id
uid=1018(testuser) gid=1003(hadoop) groups=1003(hadoop),10(wheel), 1002(hdfs) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

However, testuser still ran into "Permission Denied".

$ hadoop fs -put ./emptyfile1.txt /data/test
put: Permission denied: user=testuser, access=WRITE, inode="/data/test":hdfs:hadoop:drwxrwxr-x

Then I used hdfs account to changed the folder owner to be testuser.

$ hadoop fs -chown testuser /data/test

From the same edge node, now testuser ran put command successfully.

Here is my question: why testuser cannot write to the hdfs folder via the owner group permissions?