Well my Canadian passport clearly states that I'm MIT, so it wouldn't be a surprise to them that I also hold a Taiwan passport. It would be folly to enter the country without using your Canadian passport - you wouldn't have Canadian consular services for any issues

Recently I've asked the same Toronto "Consulate" (in person) about getting Taiwan citizenship for my Canadian born wife and son - the wife can't get citizenship but can have residency as long as we're still married. The boy can have Taiwan citizenship, but they wouldn't confirm if he would be held for military services - the attitude I got from them was Taiwan wouldn't want to draft your kid anyways so you shouldn't worry

On a different note for Beijing 2022 China has been heavily recruiting teenage GTHL hockey players with any kind of association with "China" - the gotcha was you have to "receive" Chinese citizenship, and the issue of having to serve came up.... But hey, you'll get to be an Olympian and a Private in the Red Army !!!

[Edit: To clarify, in order for my son to receive Taiwan citizenship he must apply in person @ Taiwan, which means they can pretty much hold him as soon as they hand him a Taiwan passport without an exit visa]