That measure applies only to UK and US bound flights, on UK or US carriers, at larger airports, where there some distance between 1st security check and the actual gate. The 2nd check will be more or less immediately before the gate area. Same at FRA. It's a PITA, but is carried out, apparently, at the request of the various Governments involved. I've experienced that procedure myself while PAXing on Buzz (RIP), BA, US, UA at FRA.
Never seen the 2nd search at LUX, or HHN, or on LH though
, although I have not flown LH cross-atlantic post 9-11. Maybe the extra search is on for LH to the US of A as well.