Is the MBP 15 inch with AMD Radeon M370X REALLY supported?

From what I've read, the DisplayPort spec of this MacBook does not allow for 5K worth of pixels being transmitted at 60fps. The only other 5K screen (Dell UP2715K) has to be connected with two DisplayPort cables. Nowhere except here has been stated that non USB-C Macs can support this screen. Where are the answers here based on?

LG UltraFine 5K Display

LG UltraFine 5K Display

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