The best answer I have found so far https://konstantin.blog/2012/tip-get_posts-will-suppress_filters-by-default/
It appears that setting this to true cases WP_Query to not call apply_filters() to many parts of the query. To be honest, I’m not sure what filters ACF uses, but I’ll have to assume, since it was giving you issues, that ACF does use whatever filters are being suppressed.
