Personally I disagree. There is nothing special about the World or Continental cups to justify waiving the criteria above any formal tournament, just a different organiser.
There are various examples for your list over the years, but usually they are just more examples of FAs wanting to "have their cake and eat it" by fielding weakened or "development" teams for inconvenient fixtures.
What about (for example) the recent case of Mexico playing in two different continental tournaments simultaneously?
As a famous mad scrawling on the wall of a video game
once said, the cake is a lie.
I agree there that unless something's been specifically arranged as a 'restricted' tournament, it is for a full national team. Whether the teams choose to send a full-strength squad is then up to them, and if they want to participate in two at once, then they clearly have the resources to manage the participation of two at once, the records show any 'U23' teams at the Copa America are counted as full international caps and rightly so, if that means a worse performance for the ranking of said nation if they underperform, then so be it, they picked out that cake after all.
For Luca's examples, I'd say the Superclasico and to a lesser extent those Olympics are both regarded by the participants as full internationals, and it could be argued that the 'amateur' restriction was not a hindrance to most of the teams while the culture of the time meant there weren't too many objections to that status (other than that little thing called the World Cup, but the fact they both existed as 'full internationals' for a couple of decades suggests they were both widely accepted at that level for a while at least, even after the Olympics was forced down a level there were countries (India, etc.) that considered it the most important football event)
CHAN meanwhile is a whole different beast, it has the 'permission' of the participants to be considered A but at the same time has an obvious restriction, where to begin with that one?
Fast Midfielder wrote:
Regarding Brazil. As they fielded an U-20 (some even say U-17) both
Estonia and Finland got very cheap wins against Brazil for their records
if these matches were count as A.
Going back to my earlier point, I'd say that was more 'very cheap defeats' for Brazil than cheap wins for the others. They entered a senior-level tournament and should be treated like that for the duration of their stay no matter who they put on the pitch. If a club in the Champions League puts out a youth squad for a dead rubber game and loses they can't just turn around and claim the result doesn't count towards their co-efficient.