Why does water seem to dump in the floorboard.

On my 2001 galant, I had a problem with ac water, as you described, on the DRIVER SIDE interior (you didn't mention which and the side could be passenger front area with a different cause). As the expert stated, and I'm not a expert at all but I did fix my problem on my Galant, the common problem is the area mention by the expert, the firewall. There's a TSB on this issue by Mitsubishi (Technical Service Bulletin which gives procedure for checking but light on fixing the real problem).
Back to the firewall, looking at the firewall you will have to LIFT UP the padding on the firewall in the engine compartment area (outside of the vehicle that is). If you take off the large rubber tubing for the air filter and throttle body, held on by a 10mm screw connected to a large round clamp (just pull and wiggle it off and pull the minor hose for pcv valve on top of the valve cover too) With this tube out of the way, you'll have a better view and access to the problem with ac drain spout. You're looking for a nub of a spout through the firewall ( a couple of inches long and sticks straight out). Use a flashlight if you need light, the drain is THERE. Like the expert said, the spout may have debris inside the spout, gently poke inside for blockage. The common problem is the nub drain spout DOES NOT point downwards so the water will properly drain out and not roll back into the inside of the car on the same spout ( a factory defect and other companies have done the same thing too) For your solution, after clearing any debris, is to put a short hose addition to the nub ac drain spout so it points downward 90 degrees. You may say and think, what, any tips for me on that? Sure hold on. I went to a parts store (autozone ) and go to the self-serve isle for a PCV elbow connectors, commonly used. I bought this PCV ELBOW at autozone: part # 47028 for a Chrysler. It's about a half inch in diameter and fits perfectly. I didn't use any adhesive with my elbow because the fit was perfect. There's no pressure coming out of the spout when the ac is being used. Bingo, the dealer wanted a 100 bucks to fix the problem. Now, you have the problem with your driver side carpet being trenched in water. There maybe MORE WATER than you think, padding under carpet will be harder to gauge for saturation/ ripe for mold, rust and a BAD SMELL. I recommend taking out drivers seat and rolling carpet back to the front of the BACK SEAT. Water stopped at that point on my car, wow, I said to myself, I had no idea! The drying out took around 2 days and you can till use the car while air circulates. Put the seat back in---only 4 bolts and a single connector under the seat. The degree of difficulty for this repair is easy and worth the effort. Now for the PASSENGER SIDE COMPARTMENT having water on the carpet (also another TSB) the problem is tougher to solve. The problem is BLOCKAGE from DEBRIS falling down for outside of the vehicle - the windshield wipers area (called the cowl) where air BLOWS UP from the heater/ac blower from inside the car. The cowl area has small holes in it so the warmer air can help thaw your windshield in the winter time, I guess. Debris falls through these holes and MAKES IT WAY DOWN through the AIR TUBE leading to the heater/ac blower and marches forward to the ac evaporator connecting area of heater/ac blower. This clog, forces water into the passenger compartment ;I've never seen this passenger side problem myself, but I have seen the clogging of the blower for heater/ac. You can add a "cabin filter to the blower to help prevent the problem. Check on YouTube for a video of this. Easy enough to add a filter to the blower.I did that after cleaning up the driver side problem. One was enough for me! Good Luck and keep smiling