A knock-out panel on B1 is hardly a huge cost burden; shell space between B1 and Ground does have some value, but only in so far as it impacts lost income, since the building would be there anyway.
I think its reasonable enough that the developer provide the shell space and knock-out panel and the City/TTC finance fit-out (pay for the stairs/elevator/ and finishes.
Sure, the developer can refuse, but the City can also refuse the application and make the developer appeal to OLT, at a cost that could easily run to 7 figures, then the City can slow walk permits and penalize the applicant at other locations..
There's is plenty of room for the City to make a polite ask, and take a cooperative look at options, while the developer is quietly reminded that being uncooperative could be vastly more costly than playing nice.