Great question — answering as the UphillTech team:
They still have to add it to the package. You can see the SRC code here https://github.com/Shopify/quilt/blob/master/packages/koa-shopify-graphql-proxy/src/shopify-graphql-proxy.ts and you will noticed that the version is yet not present (as of writing this answer). You can use the unstable version if you need something for the latest API or switch to the October20 one if you are not looking for something that came recently to the API.
Full answer by drip: https://stackoverflow.stackexchange.com/a/65574346 (CC BY-SA 4.0).
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