Amending req.options in a sailsjs policy

Question

I have a policy that is being used to randomly assign modified view files for the sake of split testing. In my routes.js file I have something along the lines of:

'/some-page': {
  controller: 'PageController',
  action: 'viewPage',
  locals: {
    view: 'some-page.handlebars'
  }
}

I then have a policy, splits.js that, if it detects a split test is active on this path, amends req.options.locals.view to be something like "some-split-test.handlebars". However, when the app gets to the controller req.options.locals.view has reverted back to the value assigned in routes.js (ie "some-page.handlebars"). The policy is being called and working as expected - if I log req.options.locals.view at the end, it has the updated value.

Am I fundamentally misunderstanding the relationship here between policies and controllers and their ability to manipulate req.options?