Poly in general has been relatively hard to book since the hotel side renovations - whether it's demand, Disney's booking algorithms/methodology, continued delayed rollover travel and people booking placeholders....who knows. Also October is usually a relatively popular month at WDW - Food & Wine, better weather, Columbus Day weekend is a popular fall break for many schools, and others have full fall break weeks in October.
Not sure if any are still doing this but in the pre-COVID past various travel agencies have controlled blocks of inventory in the fall and Poly CL Garden View is often included in those types of offers.
In my random searching just now there were some Poly CL rooms that popped up for late October dates, but nothing early October.
Hope that helps.