Yes, absolutely right. And this is what I have said for many years. The time window to make money on your HDB flat is very short and the 5th -10th year rule is really dependent on the neighbourhood and what you paid for it. For example in some mature estates, people have made $300K in 3 years because of demand on the resale flat they "bought". SO, it does not have to be a BTO per se.
What the clueless and Lawless Wrong has said is wrong. if you wait until you are 65 years old to monetize your flat, you have already missed the peaked appreciation in your flat. Your flat is worth less because no bank is allowed to finance any flats with less then 65 years left on the lease and even many will not do so after the flat is 25 years of age. For example, if you "bought" your flat for $300K, it might be worth $600K in 10 years time. If you cash out (monetize according to PAP jargon), you pocket the $300K. But if you stay there for 40 years or more until you are 65 years or older, no one will pay you $600K for you flat. That is because they have to pay cash for it as no bank will give you a loan. hence, at the time when you need the money from the flat the most, i.e. to fund your retirement, you find that you will be lucky to get $150K for it. Stupid sinkies better wake up to this idea.