In my opinion, as far as WS is concerned, the field is quite open, there isn't anyone particularly strong among the top 10 as anybody can beat anybody else on a good day. Besides, the top 10 aren't necessarily clearly stronger than the next 10 ranked from 11 to about 20 or so.
Not only that, both He Bingjiao and Sun Yu have proven before their abilities to defeat more than a few of the top 10 players. For example, HBJ has recently beaten the likes of P V Sindhu ( 3 out of 4 encounters, the last time HBJ beat her was at the OUE SIN Open'16 in April, the first time in Dec'15, the second time in Mar'16; however, the 3rd occasion was won by Sindhu in Apr at the MAS Open), Wang Yihan (in Swiss Open GPG'16 and in Chinese domestic tournaments as well), and Intanon Ratchanok (2x including this time) - certainly no mean feat despite the fact that her transition to the senior international circuit is barely one year as previously during her junior days she could only play a handful of senior tournaments at GPG/GP level (i,e, tier 3 BWF level) due to CBA constraints (and policies).
Furthermore, in terms of ranking as of to date, Sun Yu is ranked 11, Akane Yamaguchi, 12 , whilst HBJ herself is at 15, all of them not far below top 10, not to mention world ranking serves more as a guide than an accurate assessment of their relative strengths. Sayaka Sato at 13, Porntip at 14, Kirsty Gilmour at 16, Bae Yeon Ju at 17, Busanan Ongbumrungpan at 18, Nichaon Jindapol at 19, and Yui Hashimoto at 20, etc - we all know what they are capable of. As we know, more often than not, the ranking of players doesn't really reflect their true strengths.
What's more, the whole Japanese contingent on duty here, apart from Nozomi Okuhara ranked 5 and Akane Y ranked 12, the rest aren't mediocre at all if you've watched their games or have been following their progress, such as Aya Ohori, Ayume Mine, Sayaka Takashashi, Mitani Minatsu, Kaori Imabeppu, Yui Hashimoto.
No doubt the tournament lineup here is not the strongest for a Superseries but it's evidently not that easy for anyone to win it either in view of the available opposition. Anyway, of the top 10, there are at least four who won't be around for quite some time as two are injured, namely LXR and SN, and the other two are retired for good. Their absence will affect a number of the SS/PSS tourneys going forward, not just this Japan Open SS.
Notably, all in all, both the 4th ranked Intanon Ratchanok and the 5th ranked Nozomi Okuhara were stopped by the 15th ranked He Bingjiao and the 12th ranked Akane Yamaguchi respectively, that's telling isn't it ? So, in conclusion, I won't under-rate this Yonex Japan Open SS, even for Women's Singles category.