Whilst in essence I agree that it can be problematic that an owner or committee member is appointed as a building manager, the act does not prevent such an event.
The key issue seems to be whether or not they are owners in the scheme. This from the Act:
32 Persons who are not eligible to be appointed or elected to strata committee
(1) The following persons are not eligible for appointment or election to a strata committee or to act as members of a strata committee unless they are also the owners of lots in the strata scheme—
(a) the building manager for the strata scheme,
So, it seems an owner can be both on the committee and be a building manager but a tenant couldn’t.
Also, when it comes to the “awkward” moment when the building manager’s contract is up for renewal (or otherwise) under the amendments that came in this week the BM/member can’t be present during the discussion or vote as they have a clear pecuniary interest.