Is a prior false accusation of sexual abuse relevant in the context of a sexual assault case?

Father asserts that the excluded evidence was relevant because his "defense would have found significant support from evidence that [sister] was recounting abuse perpetrated by someone other than him." While " '[a] prior false accusation of sexual molestation is . . . relevant on the issue of the molest victim's credibility' " (People v. Tidwell (2008) 163 Cal.App.4th 1447, 1457), there is absolutely no suggestion in the present case that sister's accusations against anyone were false. The fact that sister may also have been sexually assaulted by others has little relevance to her allegations against her father.