I just tested Obsidian v1.9.12 and it does apply spellcheck to fullcaps / uppercase words (nor title case words - “capitalized” is a bit ambiguous but I think you meant the format since you mention acronyms and Caps Lock).
My suggestion is a bit related and would extend custom dictionary spellcheck to any form of casing of registered words: Option to apply case-insensitive spellcheck on custom dictionary words