Actually what that loading screen shows is 2 things, neither of which are what you accused it of being.

First you have a developer designing a game to work on a console and deal with it's memory limitations.

Second you have Valve, primarily a PC developer, not accustomed to having to deal with console memory limitations making a poor design choice in how that section of the game needed to be split up.

It's certainly no indication of a limitation of the source engine.