A Pearson-Union rail link does not mean Blue 22. Blue 22 was a specific, public money for profit private scam that had zero benefits for GO and would have essentially handed over monopoly usage of track space that should be accessible by all. Now an airport rail link operator will not have those monopoly rights and the scope of the plan has changed. Most of the money being spent will be used to upgrade the Weston line, to the benefit of GO as well as a rail link.
The EA for the Georgetown Corridor and rail link are still underway so it is still too early too say how the airport rail link will be structured in terms of ownership. It could be a private operator, or GO, or a combination of both.
It may not be perfect, but, I don't see it as being all that bad. If the small spur line can be done at a reasonable cost (and if a private operator is invovled, at their cost primarily) then this option is better than taking another 5 years, or more, to develop a plan that will allow all stakeholders to use the station and have trains able to enter from the south or north end of a Pearson station.
I see a rail link, as proposed on the above map, as an interim solution, not as anything else. A real solution willl be far more costly and complex and take some time to develop. For the moment, you at least make Union-Pearson connections easier which will have its benefits.