Mark:
That was a fairly common thought in the old days, that the bunkers could wait until later. A lot of the old Aussies believed the same thing, so when Dr. MacKenzie arrived in Australia, Kingston Heath had no bunkers at all and he was hired to suggest them.
I don't really know that waiting until later would produce different results. So much of how bunkers are placed is based on certain conventions that I doubt "observation" would overcome those prejudices.
The bottom line is that it's way more expensive to do bunker work when you're surrounded by grass (and irrigation pipe) than when you are working in the dirt, and you can waste the excess dirt in the surrounding area instead of carting it away. That's why, today, architects are paid the big bucks to take their best shot at the bunkering before the course has been played.