Javascript 导航定时API HTTP重定向等价物

我正在浏览导航计时api文档

我想了解doc所说的“或等效物”是什么意思，特别是什么等效于30X http重定向

redirectStart attribute

If there are HTTP redirects or equivalent when navigating and if all the redirects or equivalent are from the same origin, this attribute must return the starting time of the fetch that initiates the redirect. Otherwise, this attribute must return zero.