It is a very strange but good deal. The P1865 starter kit with a charger and 4A battery is on sale at $89 (which is cheaper than the battery alone at $99). While there is a special offer to give you a free brushless power tool ($99-$119 value). It is the reverse of the other offer (buying a $149 brushless hammer drill starter set to get a $99 4A battery free). The circular saw is $119 (price drop from $129) right now and the price for the reciprocating saw is the same. So you purchase the $89 (original $119) 4A battery + charger kit and get one of the saws for free. Shipping is free and you can return either item if you want. The break down prices on the receipt are $38.08 for the battery/charger kit and $50.92 for the P508/P517 circular saw. It is a very good deal for either item.
P508 Circular Saw: https://www.homedepot.com/p/Ryobi.../301848641
P1865 Starter kit: https://www.homedepot.com/p/Ryobi.../303834687
P517 Reciprocating Saw: https://www.homedepot.com/p/Ryobi.../301848739
Other brushless cordless tools are also eligible, just not as hot a deal:
3-Speed 1/4" Hex Impact Driver: https://www.homedepot.com/p/Ryobi.../301853896
Cut-Off Tool/Angle Grinder: https://www.homedepot.com/p/Ryobi.../301853890
Even if you don't need either the tool or the battery/charger, it will give you a deep discount on the item you want by returning the other item you don't need.