Such facts have been questioned, due to the alliance between Yoshimoto after he succeeded as head of the family and because Nobutora was unclear owing to the timing difference (according to Shunroku SHIBATSUJI's perspective).
しかしながら、家督相続後の義元と信虎の同盟関係が不明瞭である時期的問題から疑問視もされている（柴辻俊六による）。