I own multiple PC and on some of them, I am able to boot to Windows installer using a USB flash drive formatted in NTFS (same one for all the PC), but not for others.
PC that I have tried this on:
(able to boot from NTFS) Desktop with motherboard ASUS PRIME Z390-A and a 9th-Gen Intel Core processor
(not able to boot from NTFS) Surface Pro (5/1796) with i7-7660U (a 7th-Gen) and corresponding motherboard
(able to boot from NTFS) ASUS ROG Zephyrus M (GM501) with Intel HM370 Chipset and i7-8750H (an 8th-Gen processor)
All of them have CSM disabled (or simply unavailable) and the USB has a GUID Partition Table (GPT) and only a single primary partition.
From the information I gathered online, UEFI-based PC will only boot from an EFI System Partition or a FAT32 partition. But the evidence from my experience clearly tells me otherwise.
Why is that?