Each person/child will have different responses to different physical environments and we should all go for what will best suit our own children. I personally thought the space was refreshingly spacious, orderly and beautiful but certainly, others might think differently.
As for the certifications, however, the HK government pre-school certifications are clearly displayed on the walls at CDB. I don't think that's an issue. If the question is about an international montessori certification, I understand both teachers of the 2.5-6yrs class are trained by the highly respected AMI - but AMI is an American organization which really only accredits schools within the U.S. (some other montessori organizations routinely accredit schools outside the U.S., but these non-AMI organizations were not expressly approved by Maria Montessori).
Joanna has stated that she's seeking to get accredited as an AMI *training center* in Hong Kong, to train more adults in HK to be proper AMI montessori teachers. But this is something quite different to getting AMI accreditation to be a *montessori school* - AMI will not do that in Hong Kong and the best one can hope for here is a school that is fully committed to AMI methods. My sense is that CDB was established with that commitment.