Then I'll go to a different building. CIBC 2 and CC3 are almost as wide and are just as ready to lease as is this (if not more ready). It's a tenant's market now in terms of new Class A so why can't I / they be picky?
In the near-term, yes, a major tenant can choose between prospective building A vs B (the latter having the larger floor plate).
But if the City chose not to allow that size/shape of floorplate on a go-forward basis, that choice would largely evaporate over time; it would only change the order in which buildings go up in the nearer term.
It's really not dis-similar to the condo market where rules on mid-rises and on point towers lead to certain shapes /sizes of interiors that aren't ideal from a would-be resident's perspective.
If, as a resident you can afford any layout at any price, you'll get just that; but for the vast majority, you can only pick from the inventory available; and the City (and developers) are making those choices irrespective of
what may work for any given resident.
The same would happen with office clients.
If most space available were limited (for argument's sake) to a 12,000ft2 floor plate; then that's what you would get; unless you were willing to pay the premium for grandfathered space in the arrangement you prefer.
* note that I'm not necessarily arguing in favour of this; merely pointing out it's very possible. It's done all over the world; and Toronto can do it too, should it wish to...... (subject to provincial say so, of course, LOL)