Well you do need to use SM mode for your beginning RP in the research and the BP in the quick OOB thingy to use all yer starting points.
You also need SM mode if your creating your own race and starting system. Not to mention to get the atmospheric information back to the race's happiness levels after customizing your race's tolerances.
Every new game I make for example I just create systems til I find a world with the gravity levels I like (since you can modify just about everything else with terraforming as long as it has at least a little oxygen to allow you to create the empire.) Add HW minerals, create an empire, modify the empire to my liking, *gasping for air* then go into the race screen from the main menu, modify the race to my liking, then SM terraforming the world to the racial tolerances I set. (Usually hotter worlds about 45 to 50 C modified with CO2 or anti-greenhouse gases, with a higher than normal oxygen content) Then I just go through using up about 3/4ths of the starting RP on base techs, *gasp* then making racial techs and using up the last of the RP to research them. Then designing my base level ships and using the BP to insta build them in fast OOB creation. All of that requires SM mode, and is well within the non cheating levels of the game in my opinion. It only takes about 2 hours of your life away.
...really it's alot like rewriting the raw files for a custom race from scratch every time you want to start a new game. kinda wish you could save that kinda stuff.