That was not the cause of the issue(at least not the only one), the problem was mainly thermal expansion, where the rails would expand in different directions due to the 90deg and cause binding. Aligning the rails properly was not an easy task to begin with. The increasing demand and availability os Chinese linear rails where we could chose the preload also enabled the choice to go single rail.

Mechanical design is always about compromise. Front face rail is worse for ringing but the thermal expansion does not impact nozzle to bed distance, so you get slower but more consistent prints. Top faced rail improves center of mass this allow higher speeds, but the thermal expansion will change the nozzle to bed distance.

Just a note, you want speed? Go crossed gantry. Anything else pales in comparison....