It could be that Southgate maybe knows Livermore is a decent footballer who is being massively restricted?
Gone are the days of the Beckhams, Scholes, Lampards, Gerrards, etc English football is where it is. Livermore, Henderson, Ox, are now our standard.
Based on current form, Greg wouldnt be called up by Poland because he has been rubbish, Phillips wouldnt for scotland, Mcclean wouldnt for Ireland, Rondon for Venezualea, Brunt, Evans and McAuley for Northern Ireland, etc.
I think the national coaches see through how we play and know that there are some good footballers in there.