More than just on boot. For the brief time that I ran Win10 on an HDD, what it felt like was that the whole OS was almost constantly touching the disk, for whatever reason, often blocking. Open start menu? Better do a bunch of disk I/O. Moused over anything? Touch the disk. Pressed a key? Hit disk. Doing nothing? Disk time!

Whatever they're doing is probably fine, for very liberal values of "fine" (i.e. it's not actually fine and is probably harming system-wide performance and UX in more subtle ways, even on SSDs) for SSD-equipped systems, but made it practically unusable on an HDD.