Retire SRM (send/receive mode = monitor)?

ECMA-48 § 7.2.15:

SRM - SEND/RECEIVE MODE
MONITOR [low]:
Data which are locally entered are immediately imaged.
SIMULTANEOUS [high]:
Local input facilities  are logically disconnected from the output mechanism; only data which are sent to the device are imaged.  

Enter this mode using echo -ne '\e[12l', start cat (which appears as ccaatt) and type some text.

Backspace (^?) and ^H are handled differently than in xterm, we echo back stuff that xterm doesn't.

xterm doesn't properly echo back UTF-8 locally, produces "double UTF-8" or so.

The Linux console, Konsole, Urxvt, Kitty, Terminology, Screen, Tmux don't support this mode. (Xterm, Putty, Mlterm, St do.)

I assume this is a legacy thing not in use anymore. Can we get rid of it? :)