That article doesn't really give any good reasons for the rule to exist though. It mentions it as anti-nova protection, when that's simply not a legitimate justification, considering that other classes are permitted to nova their resources in far more extreme ways without any rules limitations being placed on them. At base, a Paladin at level 5 can nova three spell slots every turn without any limitations, and a high level paladin/fighter can nova upwards of eleven spells lots or more into guaranteed damage in a single turn. The "anti-nova" contention is a complete fallacy.
The first point is also fallacious; there simply are not any useful exploits with bonus action spells that this causes a legitimate balance issue for, and if there were, it would be a matter of errating the individual spell, and not punishing all casters everywhere. If the exploits only come from quickening other action spells for the double-cast nova, then the issue lies with quicken, which can be errataed to fix the problem without punishing all casters everywhere.
This rule adds nothing of benefit or balance to the game for existing, and it should not.
I do play in several games at the moment, and frankly, the idea that wizards and sorcerers are op compared to other classes is pretty bogus - it's a notion that comes from older generations (where it was definitely true), and they're certainly flashier for the most part... but if you want damage output, fighter, straight up, has them both whipped five ways to Sunday, and without any expendable resources, and don't even start about monks for the balance of damage and lock down... Casters burning 5th, 6th, 7th level spell slots on a damage dealing spell - a valuable and extremely limited resource - and getting less damage for it that the fighter on their regular three-strike attack, or the paladin on their double-smite, or even the rouge's sneak attack - is an extremely common occurrence in 5e. They don't need this further, counter-intuitive limitation.
I'd really just invite anyone who thinks the rule is justified to play a game where it doesn't exist, and just see; you will not notice its loss, and no-one will suddenly end up being broken or over-powered because of it. Seriously - just try it. You won't look back.