There's no way to query for an app's name with the app Id because that information is owned by the Partner who develops the app. If they don't specify their own source name at checkout and order creation, the app Id is used instead and it's intentionally generic.
The reason the name appears in the Shopify Admin is because the Merchant and the Partner make an agreement, through app installation, and Shopify makes this information visible. The app name, or any other app or installation information, shouldn't be available to anyone but the merchant and the Partner.
Beyond the privacy concerns, apps are intended to extend the features of the Shopify Admin not replicate it. Parity between what can be fetched with our public APIs and what a Merchant already sees in the Admin shouldn't always be expected.
Revisiting this issue as I don't think the answer pertaining to security or functionality necessarily applies here -- the order was created from a custom app within the storefront, not a partner app. We accept orders by phone and other feeder sites, and they're inserted into our storefront as prepaid orders. All of the order data is then synced with another system that analyzes order timestamps and locations to correlate them with TV ad spends. When an order comes in from web or Facebook or wherever, I can query the publications in graphQL and match them up. But when the order comes in from one of our custom apps, all we see in the API is an ID number under name.
Since this is all internal to our own shop, surely there must be a way to get the name we called our own app when we created it. In this screenshot, "Allegro" shows in the Admin interface. Is there nowhere in the API that we can query to retrieve that name? A list of custom apps in our storefront? Anything?