Currently I'm testing around my site and found that the sticky posts aren't showing excerpts in IOS view. (with or without the summary extension enabled), PC view has no problem. I don't have a android phone, so no way to test there.
I spent sometime searching around and found discuss.flarum.org.cn (Chinese Flarum official site) also has this issue.
On the other hand, this forum has no problem showing them on both platforms at all.
Anyone knows what caused this problem? Or did I misunderstand something?