I'm not sure if it's a restriction thing necessarily, but with DC, ya never know.
Well, here's how I see it. Warning: I have to invoke the dreaded mythos. LOL
Lois doesn't have any romantic feelings for Clark until LONG after Superman has been on the scene, saving the day. But Clark just falls for her when they first meet. Why? Just because she's a spunky reporter with a 'tude? Never made much sense to me. Lois falling for Superman? Well that makes sense. What woman with a pulse wouldn't?
I prefer the idea that Clark's feelings for Lois develop gradually over a lengthy period of time. He begins to see qualities in her that excite him in unsuspecting ways. She can read him like nobody else, and since she never sugar coats her opinions, she treats him on a direct level. And that resonates. I'm also more a fan of the mild-mannered demeanor vs. the goofy klutz for Clark, so when they're at the DP, Lois sees him as a cornpone farmboy and treats him as such. She doesn't ignore him or see him as a dumb geek.
But he's still just Clark. Lois would never have romantic feelings for Clark at this stage unless she was on drugs LOL. Clark, on the other hand, KNOWS who he kissed when his toes curled. That memory is still with him, so when he starts seeing qualities in Lois that give him a pitter patter and red eyes (LOL), he's going to be confused and flustered - because it's LOIS. He's going to hide his feelings from others and try to ignore his own feelings. Again, because it's LOIS. Sooner or later however, that attraction is going to get the best of him and he's not going to be able to bury it.
^ This is what they can actually demonstrate on SV. It will then make sense to audiences when they imagine Clark meeting up with Lois at the DP in the future. He'll fall for her instantly *because* they have a history. The very argument fans have made for why SV shouldn't have brought Lois onto the show actually explains one of the biggest mysteries later: why would Superman fall so head over heels for Lois the moment they meet? That and the glasses/secret identity thing have been conceits of the mythology. But SV may be in the process of explaining BOTH.