No, it makes perfect sense. I will put it into numbers for you but on a basic scale.
Imagine Apple only produces 100 actual watches that will be available on the 24th. Assuming that no pre-orders are cancelled here is the breakdown. Believe me, they have mathematicians that have crunched these numbers and figured this stuff out on the large scale.
They could either allocate all 100 watches to online pre-orders for people that went online at midnight and said "i want one and I am asking first". Their may even be 200 pre-orders, but only 100 of the pre-orders are getting them on the 24th while the other 100 will get them as soon as possible and no watches will go to stores. This would be the most fair way to do sales because it gives them to the first in line.
Total guaranteed sales (200)
They could allocate 50 watches to online pre-orders and 50 to stores. Then there are 150 people still waiting for their preorder online while 50 people in store purchase on the 24th.
Total guaranteed sales (250)
They could allocate 10 watches to online pre-orders and 90 to stores. Then there would be 190 people still waiting for preorder online and 90 who purchase on the 24th in store.
Total guaranteed sales (280)
If you don't believe that a company as rich and powerful as Apple doesn't crunch numbers to determine how many pre-orders they can get away with while maximizing in store sales at the same time then you are truly clueless.