>use data1 in 0
>? select() ** the esult is 1
>use data2 in 0
>? select() ** the esult is 1 ***** this result is 2 in the first code

Because it doesn't change the current WA. Simple as that. A USE x IN x doesn't move you to the x work area, just opens table x in x. Where is your first code you were actually moving to x before opening it there.

Does it make sense? This is a good thing, I don't want my work area jumping all over the place, especially like in a scan or something.