To try to answer your question as quickly as possible, the third contract was for accessibility. I believe it was also done under the national security exemption banner, which provided PSPC and the CBSA with availability to do a sole source.
The reason GC Strategies was chosen for the third contract was kind of like if you were adding scope to a kitchen renovation: You're not going to hire a net new contractor to come in, but you have to have a new contract for it. That's what PSPC said. The original two didn't have that in scope, so we needed a third contact.
I hope that answers your question.