When the class was first 'launched' in the UK, it was just intended as a 1kg (kilobot) fun class to play in by Kenny and Tom. But very quickly the popularity grew with almost everyone saying they'd build one (although there are only a few at the moment). So the conversation soon turned to standardising the class internationally so that we could compete with the Americans/Aussies/whoever else in the off-chance that there would be inter-continental battles. Long story short, the decision was made to make it an official FRA weight category but with a weight limit of 1.362kg, or 3lb (beetleweight).

It's up to you what you want to call the class. I often change between beetleweight and kilobot in posts but to be honest, it's only 300g of difference; important when you're being weighed, less important when talking about it
And as a side note, Canada opted for the 1kg weight limit. Quite a few kilobot event videos from there on Youtube.