Even if the change was due to a tax law change in Canada, the WTS MO is to always make changes appear as if they are doing for a good reason. They want to always cast themselves in a favorable light and not admit that they are dodging taxes or making changes because they are forced to. They did the same thing with removing the charge for the literature. It was presented as if this was a streamlined arrangement to the congregation, but in reality it was to dodge taxes on the sold literature. Even the change in blood fractions was likely due to pressure from the outside and not some 'revelation' or 'new understanding'.
The same applies with this change. If they had only made the change in Canada, then it would have been readily apparent that the change was to dodge taxes. By making the change globally, they can spin this as a blessing from Jehovah and a way to equalize.