It was probably a jokey summarisation from the era, but wasn’t the 188 known as the aircraft that couldn’t fly long enough, to go fast enough, to get hot enough?!
In other words it was too heavy and fuel thirsty to achieve the kinetic and surface friction heating on the trials that it was designed to carry out.

If you get the chance take your time to look over XF926 at Cosford, the workmanship involved in that stainless steel airframe construction is almost a work of art.