Will tag based search be slower on downsampled measurement?

from the Downsampling Training on March 22

Note: If you use SELECT * with INTO, the query converts tags in the current measurement to fields in the new measurement. This can cause InfluxDB to overwrite points that were previously differentiated by a tag value. Use GROUP BY <tag_key> to preserve tags as tags.

It appears that there isn’t any issue related to overwrite, but since tags are going to be fields will tag based search be slower on downsampled measurement?