Yes, the rating differs by theme quite a bit.

  +-------------------+------------+
  | theme/tag         | mdn_rating |
  |-------------------+------------|
  | Opposition        | 1725       |
  | Passed Pawns      | 1494       |
  | Rooks on Seventh  | 1408       |
  | Pawn Endgame      | 1353       |
  | ...               | ...        |
  | Smothered Mate    | 549        |
  | Stalemate         | 533        |
  | Mate in 2         | 436        |
  | Mate in 1         | 399        |
  +-------------------+------------+

I also like the idea of showing the user's +/- for each theme. Though the data for some themes is better than data for others.