I don't see why it wouldn't be intended... technically you could do it before but there would have to be an enemy underground-ish for you to jump from
and the console commands i used for jump maps were "impulse 101" bound to a key so I could quickly build my sentry, and "hurtme -90000000" for basically unlimited health. also teleporters are your friend on skyscraper... it stinks to fall down to the bottom and have your sentry base halfway up...
but everybody should do this. even more so if it isn't supposed to be possible and valve will patch it. QUICKLY WE MUST FORM THE ENGINEER ROCKET BRIGADE!
I call shenanigans Foe, no way you made it through 'All Together Now' as an engineer without nocliping. I believe thats #12. Well, thats as far as I made it. I also beat jump_rush, got most of the way through jump_pagoda and did all 5 of the cp_skyscrapers . Then I got bored and went back to regular rocket jumping