Specs are just that... specs. A 7400 is one thing, but if you designed a circuit that barely avoids oscillating with a 10 MHz GBW, an unsolicited "upgrade" to the opamp that raises its GBW to 12 MHz may be more of a disaster than a favor.

Frankly it's not OK to "upgrade" plain old TTL parts, either, since a faster 7400 might expose a race condition that never caused problems before, or cause EMI problems that didn't exist before.