When other title information is very lengthy and can be abridged without loss of essential information, omit less important words or phrases, using the mark of omission. If desired, give in a note other title information not transcribed (including the other titles or phrases referred to in 1D2).

If the other title information is lengthy, either give it in a note (see 1.7B5) or abridge it.

Abridge other title information only if this can be done without loss of essential information. Never omit any of the first five words of the other title information. Indicate omissions by the mark of omission.

Abridge lengthy other title information and statements of responsibility by omitting inessential words or groups of words. Include as many words of a statement of responsibility as are necessary to identify the person(s) concerned.

AACR2 1.1E3 and DCRB say essentially the same thing.

Is there any reason why the two rules need to be worded differently?

Consider rewording 1D4 to use the same language as AACR2.