The previous value causes the example sketches to appear under File > Examples > INCOMPATIBLE > DHTlib and also a warning to be displayed during compilation of any sketch that includes the library:
WARNING: library DHTlib claims to run on (atmelavr) architecture(s) and may be incompatible with your current board which runs on (avr) architecture(s).
Incorrect architecture value causes the warning:
WARNING: library DHTlib claims to run on [atmelavr] architecture(s) and may be incompatible with your current board which runs on [avr] architecture(s).