Hello! I'm the product manager for this area of the product and I can confirm that these metrics are identical. The process to deprecate one of these to condense this down into a single metric would have too much risk for impact to those that have chosen to use whichever one we decide to remove as a duplicate. There's no risk to our services to emit both, so we leave it as is.
You may use these interchangeably. They should always net the same value.