The iframe editor isolates block content from WordPress admin styles when all blocks use API version 3 or higher. This creates a clean styling environment similar to the site editor, preventing style conflicts from admin CSS.
Without iframe isolation, block content inherits all admin page styles including WordPress core, theme, and plugin CSS. This creates unpredictable styling conflicts and requires defensive CSS techniques to maintain consistency.
Always strive for iframe editor compatibility by ensuring all blocks use API version 3. This provides the cleanest styling environment and matches the site editor experience for consistent development.