Again, the Bootloader restriction doesn't say anything about aggregation.
The rule was, if you want OEM discounts for a Windows license the PC must actually boot Windows, using the Windows bootloader as supplied by Microsoft. Pre-install Linux, OpenBSD, BeOS and OS/2 on them if you like, but they must boot Windows, using the Windows bootloader.
Microsoft also separately asserted that OEMs mustn't sell non-Windows PCs if they want the discount. That's a much more obviously anti-competitive rule, and they've been beaten up for it on several occasions. But again it wasn't about aggregation - in this case the OEMs weren't providing Windows (on those PCs) at all.