Maybe it's just one model - the entry priced model.
"Both of these are John Deere 42″ mowers. The one from HD is a model manufactured exclusively for HD. Here’s where the problem starts. The big box stores have made deals with manufactures to supply exclusive products at attractive price points. I know there are many people who will argue this fact and say there is no difference. However, go to the John Deere site and search for Model BG20444, you will not find it. You will find the LA105 which is a similar tractor but the BG20444 was manufactured specifically for HD."
LINK
Maybe the exact same model with different model numbers. Or cheaper models. Tough to find the truth.