I'm pretty sure a player that knows anything about wiggle mechanics would be able to get out of it at 100% in less than a second, about the same amount of time it takes Lucas to recover from the lag. Connecting PK Freeze into a smash attack is only possible if your opponent doesn't wiggle out. Even at 0% it'll send the opponent too high to connect a smash before they can wiggle out. Throws don't supply much stun time like they did in the previous two games, it's impossible to connect with a PK Freeze out of a throw if your opponent DIs. If they don't DI and you downthrow them I can imagine it being possible, and in that scenario it's more than welcome as an alternative to an up-air or PK Thunder.
Aside from being able to send it over edges and being a disjointed hitbox, there's really nothing this move has over any other of Lucas' moves. If you're able to take the offensive and hit them with a PK Freeze while they're in stun for whatever reason, it would have always been possible to either use a smash, tilt, or aerial, all of which are almost always better suited for what you want to accomplish. Even though it might supply some small advantages to use as an edgeguard when the opponent isn't too much higher than you, I'm sure a competent opponent would much rather take a PK Freeze and get shot up in the air, guaranteeing safe recovery to the stage, than airdodge and risk being edgeguarded with whatever else you throw.
With that taken into consideration, it might be beneficial to use this for forcing spacing or rolls once in a while, but if you keep spamming it your opponent will realize what you're trying to accomplish and will find a way around it.
EDIT: Forgot to point out that it is capable of killing off the top at higher percentages, which is about all it will ever do other than give the opponent 11% damage and put them higher in the air.