I think some are 'made to order' under different part #s. Usually very minor changes from other tools. Just so it's harder to make direct comparison of features and cost.
They have to (now).
And also a part of big purchasers leveraging manufactures to make look a like versions with cheaper parts inside.
HD got caught and settled some civil lawsuits over that. IIRC they used the same model number but inside there was a HD stamp which gave it away when Joe Shmoe brought his dewalt drill in to the repair center. it was the business about the same model number that probably helped the class action be successful.