I think it's not a problem. It is normal to find this type of wear on a tire with knobs. On the rear tire, it is normal for it to occur due to traction. In the front it occurs due to resistance to advance. If you measure the distance traveled by both tires in a complete turn and on a hard surface and then do the same but on a non-sticky surface (like sand)... you will see that in one turn the rear wheel will travel less distance (due to skidding)... and the front one will travel more distance (by crawling)
If this resistance to the advancement of the front wheel is on an abrasive surface (such as asphalt), the wear is more noticeable.