I suspect it was intentionally trying to be free from any association/baggage connected to traditional time. Since the 'beat' time has no relation to anything physical/relate-able other than day-length, why bother keeping the baggage of UTC?
Ultimately Swatch Internet Time is tied to UTC, since it's Zurich time and not universal or entirely disconnected from the past.
If the time had been entirely separate or arbitrary that argument would hold, but the time was a normal "24 hour clock" that synced up to the standard day rotation, but centered on Zurich.
Because of that, the choice not to use UTC, but instead to UTC+1 meant that to do a calculation of UTC, which is the standard time measurement for earth, you had to subtract 41.6 beats, which was silly.
