That's not a full understanding. The point was that he'd be entitled to the title "Prince" once Charles was on the throne: it applies automatically to the children or grandchildren of the monarch. Kate and William's first born son also has it by protocol. Their later children were granted it by exception, by the Queen, even though no entitled to it officially. The expectation that - given that the three existing great grandchildren of the monarch, only one of whom was entitled to the title of prince or princess, but despite that had all received it from birth - the other great grandchildren would be treated the same was not unreasonable. To be told this wouldn't happen and therefore he would not have any protection/ security is horrendous.
You're convoluting (as did M) the issue of security and titles.
Being a Prince/Princess does not automatically mean you are eligible for "free" personal security.
Security is provided (and funded) by the Metropolitan Police (not the Sovereign Grant) and it is reserved for senior working royals who are based in the U.K.
It is "extended" when they travel abroad - where they send a team (at great expense because they have to send enough staff provide 24hr cover - so travel, overtime, accommodation etc as they can't be "replenished" from the U.K. base where the officers go home when off duty) and liaise with local Govt security for the purposes of intel and access to "threat" data.
The Palace did not remove Archie's security. They did by moving away from the U.K. to a country where U.K. police officers are not registered to carry weapons - to country where they are prevalent.
Thus expecting the Met to provide "free" unarmed police to protect them (with limited access to appropriate intelligence data) at great expense and arguably putting those officers at risk. Or presumably footing the bill for private security at a far greater cost than the Met could provide in the U.K.
Archie being made a Prince would have changed nothing in respect of the above.
The title is not a "pass" to getting the "free" security nor is it an automatic right to expect it when you choose to upturn the chess board and move to a different country from the institution (the Met NOT the RF) that provides that protection.
So no, it's not "horrendous".
It's a direct result of H&M's failure to think through the consequences of their actions.
It's also an example of people being sympathetic to their interview without thinking through or necessarily understanding the limitations of "their truth" and how they presented it.