Yes, you are correct. The purpose of automatic text color change based on bubble background color is to make sure that the contrast is proper and the text is readable. and keeping the configuration option to minimal. This is done by calculating the luminosity of the bubbles background color and checking which of black or white will be best option. However for some background colors, both black and white text colors are good enough to read.
If you think that this design configuration is very essential for your bot, we maybe able to do this customization on our end. Why don’t you drop us a line on the live chat on our website and we can see what can be done.