Remove_metrics is still valid and working in 10.5. See the help output below:
However the impact can be a little different due to the new metadata implementation using RocksDB.
Pre-APM 10.5, customers were using remove_metric to delete historical data. However, this was not the intent of this option. It is only supposed to remove the metric definition in the metadata file.
In APM 10.5 and later, if a metric is re-created again after removed, the old historical data will show up again, which was not the case before 10.5.x.
So this became an area of confusion.