So yes, that is a flush flange style install. This is generally installed into masonry with a large sealant bead backbedded on that flange, then pushed up against wall and secured with fasteners thru the interior of the window. It can be done with wood framing as well, just not as common but that is also heavily due to Florida, especially south and east Florida building materials being masonry vs wood framing...thank you hurricanes
As to the weeps, they exist on the vast majority of residential vinyl hung/sliding windows like this as its an efficient design. Works and cost effective. If the trim around it will stick proud of the exterior face of the flange, review if you can put positive slope(away from building) to reduce the risk of water pooling on the trim. This is only a concern at the sill, common building design/water mangt will have a wall flashing/head flashing over the top of the head trim, before the first course of siding goes across.
