Standing quietly and simply not reciting it nor putting my hand over my heart was never a big issue, but having to SIT for the National Anthem could bring some harassment.
In more recent years, as an adult and even as an elder, I would stand at events that had the National Anthem, ie ballgames, or community events (common at theater productions here) even with other JWs. When questioned I inquired if they were not aware that was the direction in the "new" School Brochure. Something like "when invited to stand and sing the NA, one could choose to stand but NOT sing".
I think the old timers WANTED to stir the shit! They wanted to draw attention to being different.
Calling it an "act of worship" was always bullshit. Americans stand for the Canadian anthem when Canadian teams play ball in the US and vice versa. None of those sports fans think they are WORSHIPPING the other nation.