The antibody test has many flaws including that it doesn't test for Sars-CoV-2 (the current coronavirus) antibodies, but ANY type of coronavirus antibodies. So, you could have had a different coronavirus and still have antibodies from that causing a positive reading on the test for antibodies.
I don't know how many times this must be stated, there are more questions than answers right now. Every "fact" that is stated remains questionable. There is no reason to rush back to opening until there is a better handle on this situation. Those who want to rush back to opening are putting the rest of the world who are financially and physically on thin ice at risk. Could everything be OK? Yes, that is a possibility. There is also the risk that everything will get worse. It's a roll of the dice. I don't think a trip to WDW is a dice roll I want to take with my family and my community's well-being the purse that's up for grabs.