副申請人單獨遞485隻能在主申請人485批準之後才能遞嗎？

我記得以前是說如果主申請人485 pending,副申請人也可以單獨遞485的。但我看485說明上說 "副申請人單獨遞485要不與主申請人的485一起遞，要不就在主申請人的485批準之後",不知道是不是我理解錯了?

2.Based on being the spouse or child (derivative) at the time
another adjustment applicant (principal) files to adjust
status or at the time a person is granted permanent resident
status in an immigrant category that allows derivative status
for spouses and children.

A. If the spouse or child is in the United States, the
individual derivatives may file their Form I-485 with Form I-485
for the principal applicant, or file Form I-485 at
anytime after the principal is approved, if a visa number is
available.

請問這個 "derivatives may file their Form I-485 with Form I-485
for the principal applicant" 必須是同時遞嗎？