It is here to match look and feel of AO200.
Really, the SMSL lineup could be sooo much simpler if they decided on two form factors: desktop (like da6/su6 etc) and hifi (da8 or da9 or ao200 or a300 - just pick one) and stick to the dimensions, the width at least.
They wouldn't need soo many almost identical products... There are currently 14 DACs with 300-350mm size: VMV D3, VMV D2, VMV D1se, D400 ES, D400 EX, D300, DO200MkII, DO200, SU-10, SU-9Pro, SU-9n, SU-9, SU-8s and M400 listed on SMSL site. And I am skipping the desktop units! This could easily be simplified to three or four models: Flagship ~3000$ (equivalent of VMV D3), Hi-End ~$1000 (SU-10 / D400 level), Hi-Fi ~$500 (SU-9Pro), Budget $200 (DO100 / SU-6 internals).
That would open an easy path for customers to upgrade one component at a time without sacrificing the overall esthetics of the setup. It would also introduce a bit of extra brand loyalty, as only the same brand products will retain the visuals.