About 8 years ago I worked on a new build neighbouring a large Brethren household, in fact the plot was a sold off piece of their land.
I got on extremely well with them and the bored granddad would come over to the site on a daily basis for a chat and ask how things were going. Used to talk about cycling quite a bit, they had a couple of classic tandems and he let me have a go on his old (and illegal) electric bike.
Their beliefs and lifestyle are very different, even when compared to people like Seventh Day Adventists, but I always find things like that interesting and I would ask a lot of questions which were happily answered.
I was genuinely saddened when after probably the best part of a year it came to goodbyes. So based on my experience I don’t think anyone should be put off with working with members of the Brethren. Obviously not all people are the same, but someone being a Brethren shouldn’t in itself be a reason to avoid working with them imo.