I have been looking at this myself and so far it appears the PSoC4 BLE devices only support a single channel (connection). This I actually found in the datasheets. The PSoC6 BLE link layer supports four channels.
There is no limit to the number of simultaneous connections for a BLE device in the Bluetooth Specification document for 4.2 and 5.0 versions. So this limit is actually set by the Physical layer (The controller itself) and limitations of the host OS. So as you say, Iphone may connect to 10 devices but say an android phone may not be able to connect to 10 devices. It is upto the OS also as to how you are using the resources, managing the timings necessary for BLE and also doing other functions also. So overall the entire combination of the hardware and software will decide the limit for your BLE device.
As far as PSoC BLE device is concerned, PSoC 4 will support a single connection while PSoC 6 will support 4 connections.