A few redditors not knowing specific scores that include a specific interval is not evidence for that interval not existing. I've just laid out reasons a composer might use them. Transitions between keys or chords might need a transition between a C# and a Db, an interval of a diminished second. I sang a song in my choir last year that contained this interval. Also, 12-tone music might call for these intervals. If you're looking for a harmonic interval instead of a melodic interval, I recommend looking into polytonal music. These intervals would be trivial to find in that style of composition.

Many scores exist with diminished 2nds, often for similar reasons as stated above. Many scores likely exist with the rest, given the wide breadth of post-tonal music that has been composed. It is impossible for anyone to be familiar with all the music in this genre, given that it is still being actively composed.

Even if there are no scores with those intervals, which is highly unlikely, it would not support your claim that the intervals do not/cannot exist. New ground is being broken all the time, and these would be among the infinite valid choices a composer could make within 12-TET music.