I can't find the whole executive order but this part seems to indicate that if they are found guilty before Jan 1, 2019 then the old order applies. Well there is a lot of time from being arrested to being found guilty so the arrests could begin any time. No? or is there another part of the executive order that would change this.

If the accused is found guilty of a specification alleging the commission of one or more offenses before January 1, 2019, Article 60 of the UCMJ, as in effect on the date of the earliest offense of which the accused was found guilty.