Originally Posted by kaffir76

This is purely my personal view (CAG - Changi Airport Group won't say why they do it, of course) but the reason for arrival gate checks after deplaning is so that it will lighten the checking load at the arrival hall where there are only a 2-3 giant x ray machines. We Singaporeans love to bring in contraband ciggies & what not - uncensored / pirated DVD's used to be a hot item up until recently.
(chewing gum is not contraband, by the way).
A pack of cigarettes sold here costs about USD10 so you can understand why some travelers try to smuggle a box or three in.
Of course, there could be some other security threats that we are not aware of but it's usually for intra-Asia flights from KUL, BKK, JKT etc. & if I recall correctly, only at T1 & T2.

I've never had my water bottle collected the few times I've been met with security checks on arrival so that is weird.
Won't be discussing or commenting on the rest of your post though or I may end up downtown in the slammer tonight!

And the answer to the original question by OP is no