For clarity, the O/L is unlikely to open by December 2030; its always possible, but that's certainly optimistic.
Also, the largest chunk of 'savings' in overlapping segments of the O/L an d Relief Line aren't from any changes in alignment, they are from smaller stations and lower capacity rolling stock.
I don't think we need to, and I will not re litigate the whole question of which project design is better and why; but I will make the case that you are awarding credit for achievement that isn't really merited.
Segment for segment, if one chose to go with the reduced capacity model, you could have built the R/L (meaning same alignment) and easily afforded the extension to Eglinton.
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Alternatively, based on the R/L's unit cost, had you bloated the budget by 4B, or roughly 57%, allowing for fixed costs etc, you certainly could have achieved a 65% increase in length and stations. That gets you at least 11.5km of length.
And that is also if you believe the O/L budget holds.
Ford didn't deliver any miracle or panacea, he delivered delay, much consternation, and reduced capacity with, yes, an advancement of future extensions by a few years.