I too think it would be a mistake to have the attributes @inlinable(...) and @inline(...) be spelled so similarly. The discussion in the thread on @inline(always) had mention of @_alwaysEmitIntoClient being somewhat orthogonal to @inline, but the pitched spellings here feel like a 5° difference than a 90° one—so close that they're almost parallel if you squint at them.
I'd rather we use a name that conveys the notion of "this will never have an ABI entry point" vs. "this will always and only have an ABI entry point". @Andrew_Trick 's suggestions above seem like a reasonable alternative.