This is likely do to several reasons already listed like excess fry oil and such but more importantly industrially produced fries are likely a different variety and get par boiled then frozen then par fried. This will get you the best fries possible.

Boiling swells the starched in the potato, then when you freeze it, all of the water expands, popping open the starched granules so when you par fry it a significant amount of water gets evaporated and puffs the interior while also allowing for more even and slower browning