Of course they would have been better off with T.6, as Group 4 at least did not modify the image content. However especially with TIFF there are/were countless implementations of viewers, components, libraries and every single one of them had their own habits. Some would not regard endianess, some would assume payload endianess is the same as the TIFF, some did respect the Tag for byte order specific to the image. When I coded my first TIFF Library, I was around 14 and the most troublesome part of doing it was keeping myself from bashing my head against the next available wall due to stupidity of other people who thought interpreting a standard according to their wishes was ok, because there'd never be someone trying to display the images with a viewer different from theirs.

I don't know how deep you have dived into TIFF, but maybe you remember the TIFF6 Standard way of embedding JPEG. It was the biggest pain in the ass imaginable, having to parse JPEG files, splitting them and packaging it into different TIFF Tags. Before TTN2 and easy embedding of JPEG Images, everyone invented their own way of avoiding the standard. Some defined their own compression type, some used the standard compression type, but used it in a nonstandard way, ah, I'm starting to lose my hair again ;-)