I am not sure which version of the code you are looking at. The past practice has been to maintain backward capability to the older boards by selecting features and functions that are added or changed with #define variables.
There was a significant board redesign around the transmit LPF due to the harmonic issues that were found to be caused by the wiring of that section. The board change required the relays to be wired differently. The older versions switched in the filter that was required for the band. The v5 and v6 leave the 10meter filter in the path and adds the correct lower frequency filter based on the band.
I have not seen a KT1 since I have been on this forum. I suspect it is a leftover from the single-band BITX20 and BITX40 boards or a typo that has not caused an issue so far.
BTW, there is not a K2 on the board either as that was used in the BITX40 and not in the uBITX versions. For that change, the relay that does a similar function was renamed to K3.
Above is my understanding of the information that I have reviewed. I may be wrong or have bad data. Feedback is welcome.