I found this reference in Interlace - Wikipedia, the free encyclopedia

PAL: 50 fields per second, 625 lines, odd field drawn first
SECAM: 50 fields per second, 625 lines
NTSC: 59.94 fields per second, 525 lines, even field drawn first

So I assume that 'upper field' means 'odd field' and 'lower' is 'even'. Which would mean that vegas is set up for NTSC field order, even when I select the PAL profile !

Is my thinking correct ?