Oh yeah? Well try connecting through FRA to the UK from somewhere else like GVA. No security checks in FRA at all in such cases - just walk from gate to gate - and we all remember what you can buy in GVA AFTER security!!!
I positively know that the BA gates in FRA T2, D concourse, can only be accessed via the extra security check. (The Swiss Army Knife shop that used to be in the D concourse has since gone out of business
)
If you are on LH (T1), then no, there will not be an additional security check. But then LH is not a UK airline.