Via OTRS: https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom;TicketID=11136496
"Searching for a word on a page appears to be broken. Initially it gives me over 3000
results, then I realize it’s searching for individual letters. Then it stutters for a
minute and reduces the result to three, but fails to highlight them. The latest example
was for “reverb”, which definitely wouldn’t appear nearly 4000 times on a page.
Article was Radiohead’s Ok Computer."
I was able to reproduce this on 6.3.1 1648 on iPhone XS, iOS 12.3.1