My guess is that it's a deliberate choice by the style guide. It's a frequent enough word to warrant its own acronym, but it's technically not a common noun, li

My guess is that it's a deliberate choice by the style guide. It's a frequent enough word to warrant its own acronym, but it's technically not a common noun, like "scuba." Hence the capitalization. Another example that springs to mind is "Covid" instead of "COVID-19."