2.5 Integer representation? STIX Part 1

2.5 Integer reads in part:

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The integer data type represents a whole number. Unless otherwise specified, all integers MUST be capable of being represented as a signed 64-bit value. Additional restrictions MAY be placed on the type as described where it is used.
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Is there some reason to not use the specification from RFC7159?

[-(2**53)+1, (2**53)-1]

I agree it means the same thing but why force the reader to consider what representation as a 64-bit value means? Additional restrictions are always possible, not necessary to state that here.

BTW, do you allow greater numbers than [-(2**53)+1, (2**53)-1] ? If not, then its completely unnecessary.