Connectors are not part of RS-485 standard.

As the old joke has it, standards are so good everyone should have their own:

Here are several conflicting specifications for half-duplex RS-485 on D-shell 9-pin connectors:

• Modbus uses pins 5 and 9 and 1. Standard, section 3.5
• Digi uses 3 and 9 and 5. Ref
• Virtual Serial Port uses 3 and 7 and shell. Ref, fig 3.9

If there's something common in your industry, use that. Otherwise I'd suggest Modbus, because "RS-485 on DE-9 per Modbus standard" is easy to say, easy to check, and buy ready-made cables for.

RS-485 is an electrical standard, so it does not define any connector or pinout.

So if manufacturers want to use a 8P8C connector, they are free to do so and to define a pinout they want to use with it, and there is no single correct pinout.

If you want to be compatible with standard wiring and cabling used for Ethernet, the only limitation is that the RS-485 data pins must be sent over a twisted pair, so not just any random pinout will do.

The pinout of pairs used for Ethernet is 1-2, 3-6, 4-5 and 7-8, so that is why you have seen pins 1-2 or 4-5 or 7-8 being used for RS-485. However the choise of pins 1&7 will not result into a pair of wires in standard infrastructure cabling, so that might use custom cabling that is not compatible with existing infrastructure cabling.

However, there is also a downside of using the same connectors and wiring pairs than Ethernet does. If you accidentally connect a RS-485 device data pair to Ethernet device data pair, it might damage the Ethernet device transformer with unexpected voltage and current. Which explains why one of the pinouts you saw used pins 1&7 for data pair, as it is likely that an Ethernet device survives being connected to it just fine.

Also only the RS-485 data pair between devices is not enough, a common ground reference between RS-485 transceivers is also needed, and typically one pair is also dedicated for the ground connection.