I've noticed this as well. Most of the time, they are own goals, but probably 20-25% of the time, there is a legitimate strike at goal, which the keeper would do very well to save, and when he gets a piece of it but still can't keep it out, it goes down as an own goal. It bugs me a bit, since I had never had the top scorer in the EPL (in 3+ years and nearly 2500 hours of playing the game), and I recently lost the chance in the last two weeks of the season when two of my leading scorer's strikes were ruled own goals, and he ended up tied for the scoring lead, but lost the golden boot due to the fact that he had played one more match. I guess you never do know how many got taken away from the other guy, though. Anyhow, I ended up (finally!) winning the boot with my next save.