If they do that in neutral they'll get hit by Falcon's dash attack every single time instead. On the other hand, as soon as they choose to use shield they'll get exposed to dash grab. It's mostly used for punishes though, i.e. when you cannot act, and it can punish pretty much everything in the game from midrange unless it's a foolproof safe move.
E: What comes to the Lucario matchup, I never called it 50:50, just "roughly even". might be 55:45 Falcon, but I doubt it's 60:40 assuming we're using these numbers in a way where 70:30 means hard counter and nothing beyond that is ever thrown out.
I've said this all a couple times before, but Falcon has to commit to his kills too. Bair and uair are the only non-committing kill moves which Lucario has as well, and although Lucario's bair is 6 frames slower it also hits almost as hard as the knee if he's at 100%+ aura and it's safe to throw out. Falcon has throw setups and juggles to force airdodges but Lucario has ASC to usmash. Falcon shuts down ledge getup options with jab but so does Lucario with ASC, and while you can gimp or punish Lucario after about 60% if you read his recovery, it's not hard for Lucario to gimp Falcon with his massive nair disjoint that up b won't grab through. Neutral is also scary at high percents when Falcon has to guess whether Lucario releases his ASC, shields your approach or just keeps charging it to punish Falcon's shorthop aerials which are his secondary approach option or pressure a possible shield dash-in. Neutral isn't free vs Lucario unless he's way below 100%, but with his survivability and defensive safety he's gonna be above 100% just as often as below that.
I don't think Lucario benefits from customs all that much, his default neutral b is just too good and his other customs don't seem good at all. Snaring Aura Sphere can be scary in disadvantage if Lucario is at high percents, but otherwise you can just shield dash into it on reaction and fsmash Lucario before you get hit by its slowly repeating hitbox. The ASC hitbox also comes out slower on it.