Strange behavior of `/proc/self/environ` in some shells; what is going on?

11:34   LFI to RCE via /proc/self/environ 6:29   LFI uploading shell with /proc/self/environ 5:29   Deface LFI Upload File Via /Proc/Self/Environ 3:31   Bypass Not Acceptable | LFI to RCE using /proc/self/environ 1:24   My /proc/self/environ out of sudden is readable 2:10   [Bahasa Indonesia] Local File Inclusion To RCE using /proc/self/environ DVWA 6:59   LFI to RCE via /proc/self/environ 2:57   Pentest Solution Video / LFI to RCE / Bypass Not Acceptable using /proc/self/environ 8:38   LFI + proc/self/environ = Deface 4:41   LFI proc/self/environ 403 bypass 11:27   Intranet - TryHackMe - FLAG 3 - /proc/self/cmdline 3:36   Change /proc/PID/environ after process start (2 Solutions!!) 2:09   /proc/pid/environ missing variables (3 Solutions!!)