Does "USB FS PHY / USB HS ULPI" imply double usb capabilities when using an external USB PHY?
If the OTG_HS hardware doesn't have an integrated HS PHY, then it can either use the internal FS PHY or use an external HS PHY using ULPI. A single OTG_HS hardware can't operate in both modes simultaneously.
Some STM32 devices have a OTG_HS hardware with integrated HS PHY.
Some devices may have both OTG_FS and OTG_HS hardware at the same time. STM32F407 is an example. These devices can activate both USB peripherals at the same time, completely independent of each other.
Even when operating in full speed mode with internal FS PHY, OTG_HS hardware still have some advantages over the OTG_FS hardware. It has dedicated DMA and higher amounts of dedicated buffer memory compared to OTG_FS.