Does the Smith FMS allow at or below speed restrictions?

[Driver 170]

Per the FCOM;

When modified by the pilot:

“At or above” airspeed restrictions are entered with a suffix letter A (example: 250A/).
“At or below” airspeed restrictions are entered with a suffix letter B (example: 200B/).
Mandatory airspeed restrictions are entered without any suffix letter (example: 220/).

But i’ve been told the Smith’s FMS doesn’t allow 220B and it’s probably down to operator requests.

can someone please shed some light on this.

Thanks