yep: MSA is intended to assess measurement error not process variation.
However, given that solder thickness can vary depending on the location on the board and the geometry of the pad, the OP could measure several challenging pad locations on fewer than 30 boards. The number of locations measured would then = 30.
However, given that solder thickness can vary depending on the location on the board and the geometry of the pad, the OP could measure several challenging pad locations on fewer than 30 boards. The number of locations measured would then = 30.