Why couldn't it be?
Canada has an extremely generous, massively exploited foreign worker program (it is actually one of the reasons this government is profoundly unpopular). ByteDance, like every other company, can unilaterally declare that they need to bring in an entirely foreign staff and get it rubber stamped. Given the company's alleged closeness with the party, using it as an easy vehicle to drop loads of intelligence workers of various sorts in Canada would be logical. Similarly China has a thing with running intimidation tactics against Chinese ex-pats living in Western countries.
It's not impossible, but you'd think they come up with a better front company than bytedance, of all companies. It's like China accusing that McDonalds is a spy front.
Perhaps, but China really doesn't have a lot of companies with offices in the West. When China tries to buy Western countries they are often blocked for the same national security reasons, as has happened several times in Canada.
A nondescript consumer appliance or clothing "sales office" is infinitely better than bytedance, a company that has received significant flak in the media. The Biden administration's policy of "small yard, high fence" means that unless you're trying to import chips, AI tech, drones, or battery tech, you're probably fine. Nobody is going to blink an eye at some Chinese company trying to sell rice cookers.