This was certainly the case. My grandfather, then a 19 year-old bombardier in the Royal Artillery, took part in the rearguard action on the Dunkirk perimeter. The BEF was in near-chaotic retreat, having abandoned most of its heavy equipment, Dunkirk itself was well alight, and he didn’t expect to see England again. From the German perspective they must have looked thoroughly beaten.
The German let-up (he would definitely take issue with the term “halt”) offered some of the rearguard the chance to fall back to the beaches. In his unit, one gun crew in three was ordered to hold the line, so lots were drawn amongst the men. My grandfather was one of the lucky ones: every man that stayed behind was either killed or spent the next 5 years as a POW. By the time he reached the Mole, the Germans were already through his unit’s positions and on their way to the beaches.
On the plus side, though, my grandfather came off on a Thames steamer and managed to get a hot shower and a bunk to sleep on during the crossing, so arrived on the south coast pretty refreshed compared to most of the PBI. He didn’t even get his boots wet, but then he always has seemed to manage to land on his feet!