If you refer to the MIDI Manufacturers Association Specifications,
you will see that the original specification (for 5V operation) had two 220Ω resistors in the output circuit.
The MIDI input circuit had one 220Ω resistor in series with the LED in an opto-isolator.
Thus when a MIDI output is connected to a MIDI input, there is a total of three 220Ω resistors in series, which allow a current of 5mA to flow through the opto-isolator LED.
When the MIDI specification was updated in 2014 to cater for 3.3V circuits, the 220Ω resistors in the output circuit were reduced to 33Ω and 10Ω for 3.3V operation.
The 220Ω in the input circuit remained unchanged. (So that it will work correctly from both 5V and 3.3V outputs)
The two 22Ω resistors shown in the photo, are close in value to the 33Ω + 10Ω in the specification.
If two 47Ω resistors are used as per the schematic, then the current will be reduced by about 15% (remember that there is another 220Ω in series), but is still likely to work.