If this MZO is basically just the province given the developer land-owners whatever they want, then I would imagine that the developers would request a fairly low parking ratios. Parking stalls are expensive.
I doubt the party hacks writing these MZOs have any clue what it is that they are approving, but I would imagine the developers involved and their consultants do.
First of all, I doubt "party hacks" are involved in this level of detail. I'd assume it was collaboration between MMAH planning staff and the developers (or their planning consultants which, based on the engagement materials, are Bousfields and WND).
And we don't have to speculate about the parking ratios because they're in the MZOs and I'll just paste them below. Yes, underground parking is expensive but because Langstaff Gateway is ramping up (not sure about High Tech but looks like it?) they can build the parking above ground or without digging very deep. And the other caveat is marketability - how much do the people you're selling to want a parking space? If they do, you don't want a municipality telling you you can't provide them. (And if you can sell them, who cares if they're expensive to build? 80 storey towers are also expensive to build, after all!))
BRIDGE:
(18) There are no minimum required parking spaces per dwelling unit.
(19) A maximum of 0.5 parking spaces are permitted per dwelling unit.
(20) A minimum of 0.06 visitor parking spaces are required per dwelling unit.
(21) There are no minimum required parking spaces for non-residential uses.
(22) A maximum of 2.25 parking spaces are permitted per 100 square metres for non-residential uses.
And HIGH TECH:
10. For buildings with dwelling units, a maximum of 0.4 parking spaces are permitted per dwelling unit.
11. Parking spaces allocated for residential visitors or non-residential uses may be provided as part of a commercial parking lot in accordance with the following requirements:
i. a maximum of 0.06 parking spaces per dwelling unit for residential visitors, and
ii. a maximum of 0.5 parking spaces per 100 square metres of non-residential gross floor area in the building for non-residential visitors.
As you can see, the style/organization differs between the 2 MZOs, so probably the consultants wrote them.
Anyway, 0.4/0.5 is ambitious for a suburb (and no minimums is good!) but given the number of units here, I wonder if it's ambitious enough.