A reference to how Yuzuru was in the Torrent season of 9th anniversary and Ibara and Tori were in the Spark season, making Ibara and Tori both supereffective against Yuzuru by Pokemon terms. It also fits with the fact that Yuzuru's canon, platonic love for Ibara and Tori are the exact same flavour of lovehate that manifests as condescending caring and, in a metaphorical sense, he's "weak" to them.