When screen sharing, what does "locked" mean?

When I am using Screen Sharing to access another Mac, the title bar of the Screen Sharing window shows the name of the other Mac, then a "-", then the word "Locked". What does "Locked" mean, and how can I control it?

I am using Screen Sharing Version 5.3

running under macOS Sequoia Version 15.7.1

in a MacBook Air M1, 2020

to control a Mac Mini (mid 2011)

running macOS Sierra version 10.12.6.

Another user in August 2024 said that he controlled this feature by configuring Screen Sharing to use "High Performance" mode.

"Screen Sharing is configured to connect to the remote Mac using "High Performance" mode.

I think that's what's going on is that "High Performance" mode uses a virtual display that bypasses the physical displays, and "Standard Mode" just echos what's on the physical display(s).

In any case, if I set "High Performance" mode then it says (Locked) and if I set "Standard Mode" it doesn't"

[When screen sharing, what does "locked" m… - Apple Community]

I cannot seem to find either "High Performance Mode" not "Standard Mode" in the Version 5.3 (macOS Sequoia) Screen Sharing Settings.

I did find "Adaptive Quality" vs "Full quality", but changing this radio pushbutton does not seem to change the title bar of the Screen Sharing window. It still says "Locked".

Any ideas?

--Gil