I don't really think the "nobody can do it like we did" argument works.
If it's a role the E3 is expected to do, and I don't know that it is, then they will be practising it in the sim regularly. Also the kipper fleet did do top cover reasonably regularly for single helo sar rescues it didnt however do the large scale rescue with multi agencies very often at all, thankfully. So although it was practiced in the sim, the vast majority of crews had no "Real" experience of it. I see no reason at all why an E3 couldn't perform that role.