My source is my own two eyes.
If (as your handle implies) you are French, you may not be aware of the on the spot fines because they only apply to people who cannot prove that they live or work in France. Otherwise the police have to provide for the (probably reasonable) expectation that some foreign drivers would abscond without paying.
Everyone can still appeal but, in the case of those not tied to France they have to pay a "deposit" first, which would cover the fine in case they lose their appeal and/or abscond.
It was explained to me whenI was in France that this policy is in some way linked with the forthcoming presidential elections, but I'm afraid I did not retain the name of the personality behind it....