Excellent question! While I find nothing in the Law that specifically addresses this scenario, IMHO (which, with a couple of bucks, will buy you a cup of coffee most anywhere except Starbucks) the following would be a reasonable guide:
Art. 393. Qualifications.
<snip> if a candidate has been finally convicted of a felony offense, he shall be deemed disqualified to receive the degrees. <snip>
Art. 506. Automatic Suspension Or Expulsion.
c. <snip> in the event a defendant is charged with the offense of a felony and enters a plea of guilty or enters a plea of nolo contendere and the court, after
hearing evidence, finds that such evidence substantiates the defendant’s guilt and defers further proceedings without entering an adjudication of guilt and
places the defendant on probation, such proceeding shall be deemed a conviction of a felony for all purposes relative to this article <snip>
As I read the above, I suspect that the Grand Lodge considers a person under deferred adjudication for a felony to be a convicted felon, and convicted felons are not qualified, under current Law, to petition for the Degrees.
Also IMHO, a prudent WM would contact the Grand Master & ask for his decision before proceeding any further in this matter.