Could someone help me to understand this discussion?

If I have a (in terms of timing) non critical application
and there is a PIC with INTRC-OSC running fast enough for what the program needs to do,
fine, this would save some board space.

If I need an external clock source anyway,I would not even think about RC.

BTW

for a prototype on a breadboard you could go even cheaper,
the capacitance of the breadboard in conjunction with a few drops of your favourite drink (as a resistor) at the right place on the board would also give a clock source.

But with this design don't ask us why your serial Comms are not working @ 115kbps