yes, my NanoVNA CH1 also has VSWR=1.3 at 900 MHz. You can measure it by connect CH0 to CH1 with a good quality and short cable.
Also, according to my CH0 output voltage measurement, the output impedance of CH0 is about 39 Ohm. But it may be not very precise, because I measured it with 100 MHz bandwidth oscilloscope.
