Personally I think it's stupid. I think most of these sites just do it to build up hype and attract attention. Most recent example would be Bloodborne,  practically every other reviewer has put up their review and their scores yet IGN hasn't despite getting their copy the same time as other reviewer. They do this for practically every major game and make videos talking about it instead of actually completing it.

They do it for every game, since Battlefield 4, that has an online component since a lot of games this gen have been broken because of online. Does it get annoying? Yeah, but I'd rather they be cautious then give a quick review because everyone else is doing it and then find out that they online portion isn't working well.

this.

hopefully Sony learned their lesson with DC and they doubled or tripled checked that those Bloodborne servers are working well.

I think its a good thing... Not need to rush really... Not that IGN reviews are on my care list anyway

Many many times a good game gets a bad review because the reviewer didn't put enough hours in. So IGN is doing the right thing

But if they completed the game then what else is there to do?

They are playing Multiplayer

I think they should just publish it when they are done with the game.

They might want to beat it on hardest difficulty level

Then they should do that...