I've seen the triple for a few months now for "brand" or "domain" searches but not for many keyword searches. One of my domains which I've been trying to get site links for does have several triple listing but they only show up when the domain is literally typed as the search term or the domain name is used in a query. at el; lensroll upcoming

I checked a competitors site which has had "site links" for almost a year now but cannot get a triple listing for them

I haven't done further testing on this but I tend to lean towards your thought that it's just more emphasis on domain authority.