Jose wrote:
(1) The person is now in a religion R whose only precept, Y, is true,
making the religion R valid.

... the definition of religion implied above is extremely weak. To wit:
"A religion is a set of true statements" is a poor definition of
religion. I suppose that's your point (and I agree with it). However,
R being invalid does not prevent R from being a religion, any more than
X being invalid does.

The "deductive" argument I posted was not the product of long considered
thought and in retrospect I see several problems with it. I'd rather not
spend the time needed to clean it up or defend it - or see others waste
their valuable time on debating it. You will get no arguments from me! :-)