Yup. That's why I was so disappointed with the most recent Master plan where they removed the Tran border pier (a full pier G on the scale of the domestic pier D) along with an integrated pre clearance facility. Instead focusing on the transit terminal and the assumption that additional space in the existing terminals would come from moving passenger processing to the new transit terminal.
I hate to say it but just building the Pier G would not have been nearly enough to handle the surge in transborder flights that depart every morning. Even though transborder service is the smallest portion of actual traffic running through the terminal, the F gates require the most number of gates because it has the most departing flights. Currently, there isn't an issue with the number of transborder F gates per se (they have so many swing gates running services are usually fine, it's the security checkpoint in T1 that needs more lanes), it's the international flights that are seriously running low on space. Pier G would have solved the capacity problem the hammerhead for Pier G was dedicated solely to international traffic and the Pier F gate was somehow connected to it via an underground tunnel or another moving walkway was installed heading in the reverse direction.
The question then becomes where you put all those US-bound regional flights that are still using CRJs, CSX00s, and ERJs. Pearson is in no way set up like any US airport, where most gates cater to these regional carriers, it is the complete opposite, where half of the F gates are sized for 787s and 767s (and they need to be), while the rest are sized for A320s and 737s (and I presume the NMA). The swing gates located in the hammerhead (E/F 70-71 & E/F 80-81) also have the flexibility to serve the occasional 77Ws that fly to LAX & SFO. The original idea for Pier G was designed with the 737s/A320s in mind, not the RJs, the recently constructed Pier G does this well. If they were to build the Pier G as originally designed, they would have to also build some of Pier H to cater to this requirement.
From what I gather based on my intuition, they went with the small Pier G and large Pier H because a full Pier H could cater to midsize aircraft like the 767, 737, A320, & NMA quite well, as well as have 2-3 gates that cater to the 787/777 for the transcon routes, leaving Pier G for all regional carriers, and Pier F for all international flights. This setup makes sense from a separation perspective, you could now mix the domestic and international terminals and have one large security area (like they currently do in Terminal 3), but the problem with this setup is where on earth you put the preclearance facility, getting to Pier F for all US bound travelers will be a huge pain, and getting to the Pier F hammerhead would be a really long walk. Pier F also isn't really set up for the banks the terminal usually experiences, where most Caribbean flights leave in the morning & early afternoon, and all long haul destinations (Tokyo, Seoul, Bejing, Shanghai, London, Frankfurt, Munich, Paris, Zurich, Vienna, etc) are all banked to leave in the evening. No solution is perfect, but for what they did, this one seems to be a lot cheaper.
