I think it's notable that they only ever "support unions" and not "support strikes".

Their strategy is to compete with socialists in the growing labour movement so that they can take leadership roles and steer unions away from strikes and into passivity. They will improve things significantly less under liberal leaderships compared to socialists who would squeeze them for every single fucking thing they can.

Additionally, many people in the unions themselves will want to suck up to the liberals for their "support", in many cases without it even being monetary or material in the form of labour and organising. This itself will place a deradicalising pressure on unions that struggle with it internally.