esphome does not need some external program to upload the .bin file to the sonoff. It does it all by itself.
only if you run ESPHome on the same machine that you flash it from. I don’t do that.
I have ESPHome on my NUC HA machine and I use my windows PC to flash all of my ESP’s.
If you do it like that then you need an external program.
At least as far as I know…