Fantastic post. This is something that I also find highly underappreciated, especially in discussions about the nature and sustainability of USD as a reserve currency and speculations as to the future value of the USD. 96% share among interdealer FX swaps is a pretty resounding statement about what it really means to be a global reserve currency. More than trade invoicing or relative GDP, it's about financial infrastructure/architecture.
Good post. Note that also everything is quoted against usd and bid/offer in fx swap over USD tends to be narrower than most other two currency pairs directly (ie to go from one currency to another ppl might use USD on both sides).
From my own experience, FX swap is used moch more these days now banks are required to monitor LCR on a currency basis, so dominant Eur or JPY banks have to swap more and earlier to maintain their USD LCR.
Last one, with all the excess liquidity banks also try to place with the central banks that give the best return for the lowest credit exposures (CHF, GBP, USD, JPY sometimes) when very long in their own currency. That means more fx swap turnover.