You appear to have missed this small portion of the SLA - a licensing agreement you agreed to when you downloaded and installed the OS:
B. YOU EXPRESSLY ACKNOWLEDGE AND AGREE THAT, TO THE EXTENT PERMITTED BY
APPLICABLE LAW, USE OF THE APPLE SOFTWARE AND ANY SERVICES PERFORMED BY OR
ACCESSED THROUGH THE APPLE SOFTWARE IS AT YOUR SOLE RISK AND THAT THE ENTIRE
RISK AS TO SATISFACTORY QUALITY, PERFORMANCE, ACCURACY AND EFFORT IS WITH YOU.
C. TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, THE APPLE SOFTWARE AND
SERVICES ARE PROVIDED “AS IS” AND “AS AVAILABLE”, WITH ALL FAULTS AND WITHOUT
WARRANTY OF ANY KIND, AND APPLE AND APPLE'S LICENSORS (COLLECTIVELY REFERRED TO
AS “APPLE” FOR THE PURPOSES OF SECTIONS 7 AND 8) HEREBY DISCLAIM ALL WARRANTIES
AND CONDITIONS WITH RESPECT TO THE APPLE SOFTWARE AND SERVICES, EITHER EXPRESS,
IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES AND/OR
CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A PARTICULAR
PURPOSE, ACCURACY, QUIET ENJOYMENT, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS.
D. APPLE DOES NOT WARRANT AGAINST INTERFERENCE WITH YOUR ENJOYMENT OF THE
APPLE SOFTWARE AND SERVICES, THAT THE FUNCTIONS CONTAINED IN, OR SERVICES
PERFORMED OR PROVIDED BY, THE APPLE SOFTWARE WILL MEET YOUR REQUIREMENTS, THAT
THE OPERATION OF THE APPLE SOFTWARE OR SERVICES WILL BE UNINTERRUPTED OR ERROR-FREE,
THAT ANY SERVICES WILL CONTINUE TO BE MADE AVAILABLE, THAT THE APPLE
SOFTWARE OR SERVICES WILL BE COMPATIBLE OR WORK WITH ANY THIRD PARTY SOFTWARE,
APPLICATIONS OR THIRD PARTY SERVICES, OR THAT DEFECTS IN THE APPLE SOFTWARE OR
SERVICES WILL BE CORRECTED. INSTALLATION OF THIS APPLE SOFTWARE MAY AFFECT THE
AVAILABILITY AND USABILITY OF THIRD PARTY SOFTWARE, APPLICATIONS OR THIRD PARTY
SERVICES, AS WELL AS APPLE PRODUCTS AND SERVICES.
This is from the link posted earlier:
http://images.apple.com/legal/sla/docs/OSX1011.pdf
All other arguments are irrelevant.
As for this:
the OS is sequestered onto its own drive
That makes absolutely no sense unless you have an independent and completely separate drive which contains nothing but the OS - no other apps, files, or anything else (Fusion drives do not qualify as separate drives).