Why does the Torah consistently say כאשר צוה ה׳ את משה or some equivalent after describing the making of each step of the priestly garments (Exodus 39:1, 5, 7, 21, 26, 29 and 31) but not in the context of the construction of the Miskan itself or its vessels, other than in a very general way (Exodus 36:1 and 38:22)?
Rav Hirsch, in his commentary on Pekudei 39:1 states that the individual garments were commanded separately and were considered complete as soon as they were finished and ready to be worn. The mishkan and its utensils, such as the curtains, etc, could only be considered done after the entire mishkan was assembled.
כאשר צוה ה וגו, it says this when recounting the finishing of the making of the garments, but not at the finishing of the various components of the משקן. This is only said later when the parts were assembled and the Mishkan erected in Ch. XL,19 and 21 et seq. Each separate garment was considered finished as soon as it was made. But the curtains forming the Tent, the furniture of the Abode etc., could only be considered completed when assembled and the Mishkon erected.