Old firms are now low risk therefore compared to new firms re potential nasty (and retrospective) DoTAS penalties (effectively a kind of grandfathering). See:
https://financeandtax.decisions.tribunals.gov.uk/judgmentfiles/j12234/TC...
And it's another HMRC c*ck-up of course. The nasty retrospective effect effectively backfired in this case to protect the firm re the penalty issue time limits.