I think something is lost in the translation and/or the transmission of this remark.

Look, apparent wind is the resultant of the true wind in the sail and the boatspeed in opposite direction. The last is derived from the so-called groundspeed.

So, when the current is with you, your groundspeed will be higher then in the situation when the current is against you.

This will certainly effect the apparant wind; this app.wind will increase and will be turned more to the bow (more close-hauled).

If you will lose boatspeed because of that effect, will finally depend on the boat. The boatspeed will even want to be higher because of this increased (apparant) wind (the speed was already higher because of the current).

Only problem is the direction of the apparant wind which is more and more close-hauled!