Funny, this collides with the FAQ, found here: http://support.apple.com/kb/HT4486:
How long are My Photo Stream photos stored in iCloud?
The photos you upload to My Photo Stream are stored in iCloud for 30 days to give your devices plenty of time to connect and download them.
How many photos are stored in My Photo Stream on my devices and computers?
iCloud pushes all your photos to the My Photo Stream album on your devices and computers, and manages them efficiently, so you don’t run out of storage space.
Your iOS devices keep a rolling collection of your last 1000 photos in the My Photo Stream album. From there, you can browse your recent photos or move the ones you like to your Camera Roll or another album to keep them on your device forever.
But maybe I mixed this up and 1000 pictures is for iOS only.
EDIT: Since this seems to happen to others aswell: http://www.reddit.com/r/apple/comments/1rco4d/apple_has_removed_the_1000_photo_l imit_in_photo/
I think older than 30 days or more than 1000 pictures ago, what ever happens first won't be synced. The link you gave I would interpred as limits of the stream, asuming you have turned on your mac the whole time than Apple won't guarantee that all photos are synced if you take more than 1000 per hour and so on.