Is it Best Practice to match UDP ports between internal and external realms?

I'm troubleshooting a one-way audio issue, and we think the problem is cause by internal firewall rules.  During the investigation I reviewed the available documentation and reference configurations for an Avaya connection to AT&T IPFLEX.  This comment comes from a document for Avaya connecting to the AT&T IP FLEX platformm

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7.4.3. Media Interfaces

As mentioned in Section 7.4.2, the AT&T IPFR-EF service specifies that customers use RTP ports in the range of 16384 – 32767. Both inside and outside ports have been changed to this range, though only the outside port range is required by the AT&T IPFR-EF service.

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Is that best practice, or is there any reason one would definitely want to have different UDP ports on the internal realm?