You should have 1 RCD at least, which will protect the sockets and probably several other circuits - it will have a test button on it - press the test button, if it switches off then it's OK and good to go.
The requirements now under the current regs mean on a new installation all the circuits need an RCD, but sockets are the main issue plus appliances (like an electric shower) that are fixed in the bathroom.
My guess is you likely have a split load board with half on a switch and half on an RCD - presuming the RCD works as I have described then all is well.
The type of RCD we use has also changed due to the fact we use a lot more electronic devices in our homes, and the new type is "better" in the current scenario, but we wouldn't generally rush round changing those that are out there - it only came in in 2022, so there are millions of the "old" ones still working fine!
It sounds like he was being honest with you and not trying to sell you anything, to that end I'd say he is a good electrician and worth hanging in to!!
There is a type of electrician who we in the trade call "board change artists" who love to persuade people to change the board because its a nice easy little earner - a typical domestic board costs us about £80 with a resale price of £150-£200 and it typically takes 2 hours but gets charged way over the hourly rate because its difficult technical work, but generally its not as my 14 year old lad can do one in that time to as good a standard as me!! - but your electrician isn't one of those people, so that's good!