2x isn't minraising for a start.

Open raise to 15cents, 3bet to 45cents, 4bet to 90cents. Min raise would be 45+(45-15) = 75. 2.5x would be to $1.12

The difference with 4betting is that a smaller multiplier still gets in a lot of your stack. For example, if you 4bet 2.5x here in the 5NL example you'd have ~22% of your stack in preflop, so a pot of ~$2.40 on the flop and only $3.88 in your stack which is really easy to get in over two streets.