Illustrator Scale Tool Fails to Scale Proportionally

The tooltip for the Scale (S) tool has the following tips:

- To maintain the object's proportions, press and hold Shift as you drag the pointer.

- To scale the object along a single axis, press and hold Shift as you drag vertically or horizontally.

These two obviously conflict. Sometimes the reference points I want to scale an object to are in a horizontal line, and it is impossible to scale proportionally as it defaults to scaling one axis.

Is there a way around this? Because it's such a simple thing, to constrain proportions on an object while scaling it to reference points, but seems impossible.