I noticed something similar. Often, on Horizon Q400s that are not full, they block rows 5-8 for weight/balance. On the Alaska site, it shows them as full but on Expert Flyer, it shows them blocked. This was great as I am a big guy and knowing if those rows were occupied vs. blocked was great for last minute requested seat changes. Around 7/1, that changed. Now both Alaska and Expert Flyer show the seats as occupied. Hope they fix it and change it back.