Here is a picture I dug up of a Moog Sub 37 ADSR section, you can see the position markers are different on the Sustain knob than the Attack, Decay, or Release knobs.
It’s not always made clear on other synths but the Moog Grandmother also has Attack Decay Release as knob controls and Sustain on a vertical fader.
Or the original Moog Envelope Generator 911 module shows markings for T1 T2 T3 and Esustain.
On Roland gear you’d have to read the manual but the Sustain Control is definitely Sustain Level on the Juno 60, speaking from experience.
I did manage to find a photo of a Roland System 100m ADSR module that clearly shows the Sustain control is Sustain Level.