I don't know what's Cisco's recommendation is but I can tell you what my experience has been in this regard. In most situations, any changes that I had made, similar to the one that you did, didn't require clearing the ip routes. There has been one or two situations that I had to manually clear the route(s) for the change to take effect.
I strongly believe the router should recognize the change and effect it without any manual intervention but then there may be bugs in the IOS version that's used. Though, the routes should repopulate quickly on clearing them you have to be careful clearing the routes, especially, if it's a high visibility network.