When testing iOS 15 beta we found that this occurred when code signing on a macOS Catalina system. Code signing on a macOS Big Sur system resolved this issue. I haven't seen any official documentation on what has caused this and what the requirements are, but I would love to know more. Good luck!

I'm running macOS Catalina and am having this exact issue. I've tried code signing with --generate-entitlement-der, but the -6 and -7 are still missing from the app's page size. Thoughts?

I can confirm that this works for me when code signed with macOS Big Sur. What I am hoping is (in order): (a) Code signing and app distribution isn't required prior to the release of iOS 15. (b) Code signing and app distribution is required, but can be done on macOS Catalina. Or, if neither of the above are possible: (c) Official documentation on this requirement, similar to the 'Using the Latest Code Signature Format' article that Quinn linked above. If (a) or (b) isn't possible, then (c) would at least help support change management, etc. I have just submitted a bug report regarding this: FB9318576