How can I perform Safe Boot on Sequoia system when 'boot-args' variable is not permitted?

Predicated on use byline " iMac 24″ Apple Silicon Computer

Choose the Apple Silicon method from suppled link

Restart in Safe Mode. 

If using a Mac with Apple silicon

1. Shut down your Mac.
2. Press and hold the power button on your Mac to turn on your Mac and load startup options. When you see the startup options window, release the power button.
3. Select your startup disk. It's named Macintosh HD, unless you changed its name.
4. Press and hold the Shift key, then click the “Continue in Safe Mode” button below your startup disk. 

1. 
2. When you see the login window, you might also see “Safe Boot” in red text in the upper-right corner of the login window. Log in to your Mac. You might be asked to log in again. 

We are talking of an Apple Silicon machine are we not

Review the step provied

The Machine Must be 100% shutdown - First

Not a Restart

Interesting and seems localized to this setup and or keyboard

Even my trusty $15.00 windows-like USB-A Macally keyboard on a 1 M2 and 1 M4 Desktops plus a M3 Laptop are able to boot into Safe Mode

Each machine with Sequoia 15.3.1

I just re-test on the M3 Laptop before replying your message

Go figure ?

I think this is a sequence thing. I couldn't get it to work either. But if you read the instructions carefully

1. When the Macintosh HD icon comes up click on it FIRST,
2. Then hold down the shift key; and.low and behold,
3. The Continue in Safe Mode option comes up
4. And away you go..

One shift key or both shift key work this way