Zero-volume long-tails often index faster because they combine two advantages a head term lacks: almost no competition and a precise, unambiguous intent. When a phrase is specific, Google can read exactly what the page is for and judge it relevant quickly, and because almost nobody else targets that exact phrasing, there is little to weigh the page against. The path from crawl to indexed is short when the relevance call is easy and the field is empty.
The mechanism is precision-plus-low-competition. Precision means a long, specific query maps cleanly to a single intent, so a page that answers it directly is obviously the right answer rather than one of many partial matches. Low competition means there is no crowded, established field of trusted pages the new entry has to be measured against before it earns a place. Together these let Google decide the page is relevant and worth indexing with little friction, which is why the page appears in the index sooner than its search volume would suggest.
Head terms behave the opposite way, which is the part that surprises people. A short, high-demand query is contested by many established pages, and its intent is often broad or mixed, so Google has to work harder to decide where any new page fits and whether it deserves to be shown at all. The page must prove more before it is indexed and ranked, not because high volume makes a term important to index first, but because the crowding and ambiguity slow the relevance judgment down. Volume does not buy speed; clarity and open space do.
Use this when you want early traction. Target winnable long-tails with clear, specific intent for your first pages on a topic, get them indexed and earning small traffic quickly, and let that early footing support the harder head terms later. The lesson is that fast indexing follows precision and open ground, so write for the exact question first and chase the crowded terms once you have a base.