Ssh – Why would pgrep not show the processes but sudo pgrep does

I looked at a list of processes and filtered out ssh-agent which correctly shows the 3 processes I expected:

$ ps -ef | grep ssh-agent
belmin   1051     1  0 16:05 ?        00:00:00 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
belmin   2569     1  0 16:09 ?        00:00:00 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
belmin   2655     1  0 16:09 ?        00:00:00 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
belmin   5093  2596  0 16:17 pts/1    00:00:00 grep --color ssh-agent

However, if I perform a pgrep, it doesn't list the 3 processes unless I escalate to sudo:

$ pgrep -a ssh-agent

$ sudo !!
sudo pgrep -a ssh-agent
1051 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
2569 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
2655 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple

Initially, I thought it was because PPID is 1. However, this isn't a problem with other processes that have PPID as 1 so that's not it.

What am I missing here?

Update:

So apparently applying namespace argument (--ns) works without sudo—regardless of what namespace I provide:

$ for n in 'ipc' 'mnt' 'net' 'pid' 'user' 'uts'; do echo pgrep -a --ns $n ssh-agent; pgrep -a --ns $n ssh-agent; done
    pgrep -a --ns ipc ssh-agent
    12986 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
    pgrep -a --ns mnt ssh-agent
    12986 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
    pgrep -a --ns net ssh-agent
    12986 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
    pgrep -a --ns pid ssh-agent
    12986 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
    pgrep -a --ns user ssh-agent
    12986 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple
    pgrep -a --ns uts ssh-agent
    12986 ssh-agent -a /home/belmin/.ssh/.auth_sock.pineapple

Still unclear as to why. I'll keep digging.