Being Chinese-Canadian, I've also had some experience in pharmacies and traditional chinese medicines shops in Hong Kong. It's not malaysia, but it's not like i'm completely blind to poor work practices. Dexamethasone is not a naturally occuring substance, it's something that must be synthesized, and the distributed. No matter how you spin it, the likelihood of some controlled substance, different working practicec in different countries or not, is unlikely. Dexamethasone still come in their own bottles, unless you're telling me that a Chinese herbal shops in Malaysia just grinds up some dexamethasone tablets and just blow it through the air, contamination really shouldn't be an issue. I'm not being rhetorical, I genuinely can't think of a way for dexamethasone to accidentally contaminate LCW's herbal capsules. The only situation is that he put both in the same container, which means that it has nothing to do with pharmacy practice and just personal cleanliness.
You may say I have no understanding of less economically developed countries, and you'd be right. Unlike street food, controlled substances all have packaging requirements for the sake of the medication. It's in no manufacturer's benefit to make dexamethasone and just sell it paper bags.
Drug manufacturing is designed to hit as many markets as possible, regardless of where they're manufactured. Therefore: drugs are almost always contained to at least bottles or blisters, to stop them from deteriorating = lower chance of contamination.
Another point, Usain Bolt is a multi-millionaire, celebrity, world elite athlete. You can argue he comes from a fairly poor country, (for reference: Canada GDP/PC:51000 USD, Jamaica GDP/PC:5,200 USD) and Jamaican pharmacies probably don't conform to the same standards. Do you genuinely believe him being a multi-millionaire with a training staff, health staff, technical staff all to support him are going to allow him to go to random pharmacies with dexamethasone blowing through the air? The answer is a simple no. You don't have to know Usain Bolt personally, or know Jamaica's pharmacy practice to conclude that Usain Bolt isn't going to random pharmacies.
By extension, same goes for LCW.