those that say 'can' because they want your buck.

but no it is not 'allowed'. There was a 'way' previously but authorities has been eyeing their operandi.
*you may ask why is it not allowed?

it has something to do with protection on the local market + several reasons. Many SG cars are generally quite 'low mileage in a way'. The SG LTA made sure cars over a certain number of years are....well, not worth while to keep, just $$$. (while there are those who still wanna keep certain classics)