Subdomains are, per current Google guidance and observed behavior since the shift toward domain-level ranking signals, generally crawled and indexed independently of the root domain. A site at {slug}.bigideasconnect.com won't meaningfully inherit the root domain's authority or backlink equity — Search Console treats it as a distinct property, and it effectively starts cold, the same as a fresh root domain would. There's no "free ranking boost" from being hosted under a bigger domain.
Crawlability isn't the concern
Pages here are server-rendered at publish time, not a client-side React shell requiring hydration before content is visible. We've verified this directly: a complete document delivered in a quarter of a second, real headline and body copy present in the initial HTML response, canonical tag and OG tags server-rendered, JSON-LD present. Googlebot's initial fetch already sees full content — no dependency on a second-wave rendering queue, which matters for crawl efficiency independent of the subdomain-vs-custom-domain question entirely.
The real lever: canonicalization and domain equity
Once a client's custom domain is CNAME'd and verified, the site is automatically redirected — a real server-side 301, not just a canonical tag — so it serves under and is indexed as the real domain going forward: full first-party domain authority accrual, a real backlink profile, real E-E-A-T signals, fully decoupled from the platform.
Practical recommendation: treat any pre-custom-domain phase as staging, and prioritize the domain cutover before any serious link-building or content push. Links built pointing at the subdomain still transfer via the redirect, but a same-URL-from-day-one approach avoids the question entirely.