Transmission Cooler Bypass?

[Roadmarks]

Howdy, I have added an external trans cooler and filter to the nose of my '71 C10. The outfit that I got It from, Makco Distributing, strongly suggests a "cooler bypass" for very cold starts. I don't mind adding it if it is really needed, but the original "in the radiator" cooler doesn't seem to need it. Are these guys just trying to stick their hands deeper in my wallet, or do I need to look into this further? My flow pattern will be through the filter then original rad cooler then through the add-on cooler. Comments or thoughts?

Thanks