I actually looked a lot more at 1.d4 d5 2.c4 e6 3.Nf3 dxc4 4.g3 and it's really not that bad for White (even in the c5 lines). A lot of lines have the potential to transpose back too.
It's an equal game but White has a bit of initiative, a lot of Catalan themes and way less forced play than in the 4. e4 lines. Were your opponent to know the e4 lines, he can force the game to very drawy wters (unless you're willing to be worse as White).
It can also have endgame lines but they aren't as forced. For example:
1. d4 d5 2. Nf3 e6 3. c4 dxc4 4. g3 c5 5. Bg2 Nc6 6. Qa4 cxd4 7. Nxd4 Qxd4 8.
Bxc6+ Bd7 9. Be3 Bxc6 10. Qxc6+ bxc6 11. Bxd4 Bb4+ 12. Kf1 Nf6 13. Kg2 O-O-O
14. e3 Rd5 15. Bxf6 gxf6 16. Rc1 Be7 17. Nc3 Ra5 18. Ne4 Rb5 19. Rab1 Rd8 20.
Rxc4 f5 21. Nc3 Rb4 22. Rxb4 Bxb4 23. Rc1 Rd2 24. Na4 Kc7
It's kind of funny though that every time I study an opening in depth it turns out to offer nearly nothing for White if Black plays the main defenses. I might as well play the Colle or something and just know from the start I won't have an advantage!
To be fair, more theoretical openings tend to have way more pitfalls in the positon, more tension, and can punish big mistakes harder. This was my problem with 1. b3 during a stint with it. The positions were fine but I'd get random moves like 1. b3 a5 and STILL couldn't pounce on them or do much. Literally almost any move Black continued to be equal. If you go 1. e4 and your opponent goes a5, he will have a hard time withstanding your initiative.