IIRC, that initial “don’t use surgical masks” statement was because hospitals were already facing shortages, and a rush on the supply would have caused massive widespread longstanding shortages. Basically, the hospitals needed disposable masks, so the CDC told people not to use disposable masks.

But it was also in that brief time period between surgical masks and reusable cloth masks. So the messaging was basically just “don’t use disposable masks” because the “disposable” part was implied because it’s all that was commonly available on the market. Plus cloth masks hadn’t been studied yet. So when cloth masks were proven to work and the CDC started recommending them, the naysayers fell back to that initial messaging from when the cloth masks were unavailable and unproven.