I have a mini device that plays this version of the game

lego

@tent2 Your first hunch is right. Done a bit of research. Firstly the game has the standard Sega cartridge unlike EA, Codemasters and a few others and both the covers/cartridge says Manufactured by Sega. Secondly it uses the Official Genesis Seal of Quality that Sega of America used at the time. Had it been unlicensed like Accolade, they would be a notice saying something like "Not licensed/endorsed/associated by Sega". Just like they did on a printed advert for the game but for Nintendo, weirdly there was no mention of Sega on there. This might be the source of confusion where the NES game is unlicensed.

Also the game has two publishers, Tengen in the US and Domark in Europe (credited at the back of the box as "Sales and Marketing"). Domark was a licensed publisher for Sega as they had brought out some Master System games (Klax, Super Space Invaders) when this came out.

There could be an argument made that the game doesn't have the standard Sega logo bootup. This would put the game in the same category as EA and Codemasters, licensed but had some free way.

@ilovescratchcie That's right. Whoever uploaded this game must've thought it was the NES bootleg.

Edit: Uh, nevermind. After a bit of research, it turns out this is unlicensed, therefore it is a bootleg. I thought it was official because upon googling it this game is listed as part of the Mega Drive alongside the other consoles this game is actually officially in.

It's not a bootleg