It could, and probably did, fill up the oil breathing capabilities of the engine, and you will "Play the Devil getting them cleaned out."
To wit: A man brought his vertical shaft lawn mower in, and said:"I changed the oil and now i can't pull the starter rope!"
Upon further checking, i found the engine oil clear up to the top of the dip-stick tube!! WOW!
I then set upon trying to get the excess oil out of it, but after several days of trying, i finally gave him the bad news. After giving an estimate of time to fix it, he just gave it to me. I never could free it of the excess oil, so i installed a used engine, and sold it.
I had wondered when he told me it took a whole lot of new oil--much more than he had drained out of it--to fill it up! HMMM!
So-how much oil did you put back in it? Did you follow the recommendations of the engine mfgr? I'd say it seized up from eithr too little oil, or too much. Both could cause problems. A little extra might have sufficed, but never put too much more than the right amount!

I would remove the spark plug and then see if you can turn the engine over. Last year i bought a brand new mower with a seized engine that had been overfilled with oil causing a hydraulic lock. Bought it from a business that does warranty work for one of the big box stores. Had been written off as unrepairable.

What brand engine? Chineze IMport? First off was the engine on the tiller installed where it don't set level? If so you must check the oil in the level position. You may have to use a level to do this. Now if the LOPW Shuts the engine down. and you rechecked the oil in the level position and it was still in the XXXXX or at the top of the dip stick or plug IMO it would be to the severe angle when you operate the tiller with the engine tilted caus ing the switch to activate do to no oil at that end of the crankcase sump. I would of done two things, First figure out if I had a pressure lubed engine. Then disconnected the LOPW switch and run it. Next would be a defect causing this problem, too much oil, internal, or by mounting an engine that oil system wasn't designed to be ran unlevel position?

Be careful. My 1983 Horse requires (factory notice) that I put the drag bar all the way down and then put a 3 1/2" block under it, besides. Check the manual, or find out the proper volume and mark the stick.