Found the total opposite, in the mid 2000s, the polish where better than the useless English people they sent. There were two off us who were English and went agency - full time. Agencies sent both English and polish. Polish weren't amazing, but they worked and stayed. English usually didn't last one shift. Generally a bunch if lazy creations that want money for nothing, and couldn't put up with a bit of muscle pain for the first few weeks.
I can gully understand why some companies would prefer polish.
Is it better going trough 20 English to find one or two very good workers and be left shift after shift short handed by the utterly useless work ethics.
Or have steady staff that work, albeit it at not top level. But at least they will be there on time and they will work.