The intent, in my very strong opinion, is that you don't muddle the "Casting a Spell" rules with a literalist, RAW interpretation of the "Readying an Action" rules. My strongest objection is that we're choosing the literalist, RAW interpretation in one instance and then reconciling the obvious problems with that interpretation by an appeal to "intent" where it suits us.
And here is where we often get in trouble applying 3.5 mindset to 5e.
In 3.5, the game was built around a "legally stringent" version of the rules. The rules were designed to be the primary judge and jury, and the goal was a rule to cover as many scenarios as possible. Part of this mindset was that the rules were designed to be very cut and dry, and very specific. So in any case where things were debated, it was pretty reasonable that anything stated by RAW was often RAI....as the designers had taken the effort to right very specific rule sets. This is also why 3.5 had a lot of errata, any issue found was updated in the text again to keep it a clear legal record of how the gameplay was intended from the designers viewpoint.
5e pushes the arbitration more on the DM, and uses a "guidance and framework" model. The rules are more designed to get a DM comfortable handling various scenarios, and then the DM can take on the rest of the work of interpreting scenarios and applying reasonable rulings. This combined with the natural language 5e uses makes the rules a lot fuzzier. The reason that's important, while we can have this RAW arguments (which I found rather fun), it is harder to then take RAW and apply a RAI from the designers. The simple truth is, 5e's language is fuzzy enough that there are many cases where even though the rules say X, we can't really tell taht the designers imply X (whereas in 3.5 we could at least make that a reasonable starting point unless the devs directly spoke up and countered it).
All of that is a longwinded way of saying....just because we can make a strong RAW argument, we really can't say, "and therefore, that's what the designers intended".
The truth in this scenario is....the rules of casting are murky. There is no defined start and end point, and the nuances of a readied spell are murkier still. My guess....is that the designers didn't even consider the idea of readying a spell to avoid counterspell, it probably wasn't a discussion, and I doubt they wrote the ready rules with any notion of how it would be used against counterspell.
So there is no "official method" here, its just a question of which one is better for the table. Though I think I have made a good RAW argument to say why readying a spell doesn't stop counterspell....the real argument is....its just very cheesy and jenky. I think counterspell is too powerful, I hate the spell personally, but if I'm going to stop it, I would rather nerf or ban the spell than allow some jenky tactics to overwrite it.
