This is wrong. The plan was to do something very similar to what Man City did. In fact, the original plan for this is outlined in planning documents for the new stadium
In the Spring of 2017, with the support of Liverpool City Council, Bramley-Moore Dock was identified as a potential site for the athletics venue of the 2022 Commonwealth Games bid. As a result, Everton commissioned a feasibility study for phasing a stadium construction that could accommodate an athletics mode for the games. The stadium, built on an east-to-west orientation, would have held 40,000 spectators in athletics mode and finally 60,000 as a completed football stadium.
Once the CWG bid was dead, the plan was reorientated North-South, which is the orientation football stadiums are normally built with (for reasons to do with the sun, broadcasting etc). This is a bit more of a tight fit, so capacity ended up being constrained.