The distinction is important: a change in a law isn’t always a slippery slope towards other things. Implementing congestion pricing isn’t a slippery slope towards seizing peoples’ cars, which was GP’s point (which I agree with).
To make it obvious: universal suffrage is a change that happened, but it wasn’t a slippery slope towards giving dogs the right to vote. Some changes result in new stases.
But nobody was claiming congestion pricing would absolutely lead to seizing cars. The OP was talking about the fear that more things may happen, which is perfectly logical. Today, nobody (including you) can say whether 10 or 20 years from now, ICE cars will be banned. But observing steps that appear to lead in that direction, and being concerned or fearful, is rational and logical.
To make it obvious: universal suffrage is a change that happened, but it wasn’t a slippery slope towards giving dogs the right to vote. Some changes result in new stases.