I'm posting this in both 16 and 15.6 beta threads.
iPad Pro 11 2020 - 16.0 b1
iPhone 13 ProMax - 15.6 b2
I've posted in both the 15.6b2 thread and the 16.0 b1 thread on this issue - slow to launch apps; my OnePlus 9 Pro is quicker.
The 13 ProMax is OTA
The iPad Pro 11 was OTA then ipsw.
Both suffer from this issue.
Spent some time comparing both devices on Wi-Fi (6e), 5G, LTE, and in Airplane Mode.
1. If the app is native and runs only native it is very fast.
2. If the app queries the internet or does a guick pull it is fast irrespective of Wi-Fi, 5G, or LTE.
3. If the app pulls/fetches from the internet and has a live link (up and down) it is slow. Doesn't matter if it is Wi-Fi, 5G, or LTE. Once it launches and is up and running (ready for use) it is generally very fast.
For #3, I'll use Proton Mail as an example, if I place the device in Airplane Mode it is fast. Turn off Airplane Mode and it crawls at launch.
This does appear to fit into on again - off again issue many of us are seeing with Wi-Fi. If it was the internet site/source or Wi-Fi, 5G, or LTE, I would be seeing this across all my devices (OnePlus 9 Pro Android 11, Lenovo X280 Ubuntu 20.04, Lenovo X280 Win10 (x2), Galaxy Chromebook, MBP 2015 Monterey). I'm not. Everything is running great on all but the iDevices.
Here is to hoping that Apple eventually fixes this issue.
I have posted Feedback.