(Sometimes you'd have the arrangement where there's token opposition that is similarly nominated, much like DPRK today.)
As for people going to vote, that was actually enforced. While there was no law about it, strictly speaking, not going to vote would likely earn you a reprimand at work.
In Soviet elections, most ballots had a single candidate - the one nominated by the local party committee. Typical example: https://ru.wikipedia.org/wiki/%D0%A4%D0%B0%D0%B9%D0%BB:Ussr_...
(Sometimes you'd have the arrangement where there's token opposition that is similarly nominated, much like DPRK today.)
As for people going to vote, that was actually enforced. While there was no law about it, strictly speaking, not going to vote would likely earn you a reprimand at work.
That's the point. "Allowing elections" is not enough.