Glad you enjoyed it. Yes, the tritone can be considered a bV (or diminished 5th), but my reasoning for calling it a sharp 4 is that when modding the scale (minor), you sharp the 4 while the 5 still remains in the scale. Also, It's easier for me to read it as [I, II, bIII, #IV, V, bVI, bVII] than [I, ii, bIII, bV, V, bVI, bVII] as we have a distinguished number for each interval (rather than displaying 2 Vs we read the intervals in succession as IV, V).