The 'Get Custom Reward Redemptions' Endpoint requires the call to provide a reward ID and a redemptions id/status. This means in order to get a list of the last 50 channel point redemptions for a channel, you have to do a separate request for every single reward available on a channel.
This seems way over complicated to just get the last redemptions on a channel.
Ideally, you could call this endpoint and get the last 50 redemptions that include redemptions of any of the rewards. Then a parameter of offset could be provided to get more redemptions.
Not sure why this wasn't the way it was made initially, but this would make it much easier to use.