I believe withheld means if they have a probation agreement and pled to a lesser charge, then they avoid the felony charge.
Problem is, they’ll just make what few crimes aren’t felonies a felony to charge up the accused and scare them to plead guilty to avoid a felony.
Typically when a conviction is withheld the Judge does not accept the defendants guilty plea. The defendant is given a stay of adjudication where the plea is not accepted and conditions are set, similar to probation. If a defendant fulfills all of the conditions during the time period set by the Court, the charges are dismissed. There is no conviction on the case and the person is not a "convicted felon". If the defendant violates the conditions, he is brought back into court, his guilty plea is accepted and he is convicted and sentenced.