That's correct.
It's fair to say, and the courts have clearly held this, that when you impose an obligation on the defence, the requirement to do something assertive to avoid conviction—and that's what strict liability does; it imposes on the accused the obligation to prove on a balance of probabilities that they met the appropriate standard of care in trying to avoid the prohibited act—limits the presumption of innocence that's guaranteed under the charter. However, all guarantees under the charter are subject only to such limits as can be reasonably and demonstrably justified in a free and democratic society.
So yes, there's a limitation of the presumption of innocence when you impose a reverse onus, but those limitations can be justified, and the courts have generally held that they are, in a regulatory context.