Ah but then you do, Dale. Channel 5 is 462.6625 MHz. This is an interstitial channel as defined by 95.1763(b). The antenna/power allowance for this interstitial group is different than that I previously cited. 97.1767(b) limits the GMRS ERP in this case to 5 watts. It is worth noting that this is different than a GMRS certified radio which is limited to 2 watts ERP per 95.567.
So you are still stuck with having to compute your ERP with your antenna of choice if it is not the stock antenna that came with the radio. And you probably won't convince your instructor of how right you are once you have done that.
Regarding your other question, 95.1787 lays down requirements for the manufacturers that wish to have product certified as GMRS data transmitters. This does not directly affect you as the licensee/user. Due to other regulations, you are not allowed to modify permanently attached antennas, for example.
Note that these requirements for certification change from time to time. Unless the regulations specifically disallow you to use a transmitter certified under older regulations, you may continue to use it. So for example, if in the past a manufacturer could have a detachable antenna for certification but now they cannot for new certifications, you could continue to use the old version as a licensee since there is nothing in the regulations prohibiting you from doing so.
- Glenn W9IQ