ah, PDE/PTE A/D writes... what a source of variety over the decades!

some chips set them step by step, as shown in the article

others only set them at them very end, together

and then there are chips which follow the read-modify-write op with another read, to check if the RMW succeeded... which promptly causes them to hang hard when the page tables live in read-only memory i.e. ROM... fun fun fun!

as for segmentation fun... think about CS always being writeable in real mode... even though the access rights only have a R but no W bit for it...