it was allowed in years past because it was a "C". I believe this year the updated the code making it a D. I had most of my 8's doing it last year, but none this year. I'll ask the the beam coach I tend to forget most beam code
Same thing happened to the aerial, which was getting more common in L8 before it was changed to a D. You can't do Ds in L8 without penalty and a D in L9 is effectively counted as a C for connection purposes because there's no difficulty bonus and C+C qualifies for max connective so basically all a D can be counted as is a C. A "D" value beam acro skill like a layout will void the exercise in L8.
About 4 years ago, the layout stepout was valued as a C. Level 8s could do C acro skills and therefore there were some gymnasts who competed bhs/blo as their beam series at level 8.
Two years ago, the layout stepout on beam was upgraded to a D. Up until this year, only C acro was allowed at Level 8 so the layout stepout disappeared in Level 8 beam routines when the layout stepout became a D.
Beginning this season, the layout stepout is back to being valued as a C. Another change this season, however, is that level 8s no longer can do C acro on floor and beam. Therefore, the layout stepout continues not to be allowed at Level 8 (it is a C, Level 8s cannot do C acro) although for a different reason than in the past.