The idea is that less severe crimes can be handled without the full overhead and without excessive punishment. In practice, this can be 'a bit' controversial, e.g. when Bernie Ecclestone resolved his corruption charges this way by paying 100 million EUR. https://en.wikipedia.org/wiki/Bernie_Ecclestone#Bribery_accu...
I don't know enough to comment on if this is something that happens often (it certainly doesn't feel appropriate) in cases like this.
> If the parties agree that the recommended fine needs to be paid in installments because of the defendant's inability to pay the entire amount immediately, the plea agreement will include the installment schedule and any interest terms.(58) The payment of a special assessment(59) and any recommendation on a term of probation(60) or expedited sentencing(61) for corporations, or requests by individual defendants to be placed in a specific correctional facility,(62) will also be addressed in the plea agreement.
https://www.justice.gov/atr/speech/us-model-negotiated-plea-...
And to get back to the original comment I replied to, this critique seems like it would apply to any financial punishment, not something that came down to a technical distinction between "fine" and "financial penalty".