I don't think that a meltdown Vs tantrum can be defined by whether it stops by meeting a need. I think it is more to do with how much control the person has over their behaviour during the incident and how aware they are of the effect of their behaviour on the people around them.
Classic 'toddler tantrums' are often quite funny to see, because you get the periodical "effect check", where there is a slight pause, looking to see what Mum/Dad is doing, sometimes even a deep intake of breath, before a renewed effort to go all out with the kicking/screaming/yelling.
Older kids tantrumming tend to escalate in levels. They start with the mild pouting, move on to the lip wobble, the stamping of feet, the threats, insults, etc. It can get quite extreme, but it's logical and the child 'knows what they're doing'.
Meltdowns are different. They can be quite terrifying for both the person having them and the people dealing with them. They are emotionally exhausting. They are irrational, in the sense that the intensity of the meltdown doesn't necessarily correlate with the cause.
I don't know about Fortnite - I don't think I'd be keen on a 9 year old playing it. But if he does play it, then essentially, he was saying "I need to chill out".