In Kicad 5, an electrical rules check of the schematic would flag an error because although the net on pin 1 of R1 has a label, nothing else has the same label, so the pin is not connected to anything. If this was the intent (for example to assign a net class to the pin, which requires a label, but leave it unconnected), then the solution would be to attach a no-connect to the end of the wire.
Kicad 6 seem to be treating this differently. Without the no-connect, it accepts the circuit as valid. Apparently it’s treating the label as if it represents a connection. Indeed, if one puts a no-connect on the wire, the ERC flags this as an error where there’s a no-connect with a connection.
To my mind, Kicad 5’s treatment was correct, and in particular would pick up mistakes where there’s a mismatch between the labels that were meant to connect a net.