This is only partially true. If miners activate a soft fork - say op cat, and no nodes update then you get a chain split. Miners fear this because it would be a massive headache for them and likely reduce their revenues. Admittedly if there is a miner activated soft fork you don’t need a majority of nodes to update, but you do need a significant amount of them. That threshold is unknowable in advance but I’ve heard it theorized around 20-25%.