I think it depends on the adjudicator......
If he is a screwy guy...he may issue an RFE....
Bottomline, there is no reason for them to issue the RFE for EVL (Employment Verification letter).....The only reason they issue it - there is too much itch up the adjudicator's AS*....
But, yep, bunch of address changes may the only clue.....for adjudicator....other than that - he really has no info (or may be H1B transfers - if he bothers to look deep enough) at his disposal to make the judgement call on issuing RFE....
Or it may be like....too many years...in adjudication....may be one reason....