As DCT Does Compaction of Energy, Can We Say IDCT Does Energy Spreading?
For certain kinds of signals (voiced speech, most music, etc.), the DCT is likely to compact, and thus the IDCT to (re)spread that more compact DCT result; but that is not true in general.  An impulse in either domain will be spread in the other domain, and vice versa, for that spread result, when inverse transformed.