Yes, they can be wrong. They don't have the charism of papal infallibility. St. Thomas was wrong about the Immaculate Conception, and that was in the Summa.
No one is pretending they had such a charism, so that point misses the mark and only serves to muddy the waters. Furthermore, the IC was defined centuries AFTER St. Thomas died; that is not the case with EENS, neither in the case of St. Thomas nor St. Alphonsus.
You are basically positing the idea that two Doctors of Holy Church speculated erroneously, maybe even in an arguably-heretical manner, about a well-known dogma --
perhaps the most well-known dogma of all -- and that is perfectly acceptable. How can that be so?
Water Baptism is either absolutely necessary --
no exceptions whatsoever -- or it is not.
As I mentioned before, please refrain from discussing or worrying about the modern insanity; stay focused on the two Doctors in question. Thank you.
FWIW, a joke is a jocose lie.