The rings are never touched during a head job, that is a much more involved process.
If they did a leakdown and a compression test, and the numbers came up normal, this is a mistery.
I will suggest to change your oil to a heavier weight 15W-50 or 20W-50 and see what the results are.
I have been running 20W-50 for years, and it consumes about a quart every 1500-2000 miles. The compression is really good, and the sparkplugs are dry. I have never seen a puff of blue or gray smoke coming out of the exhaust.
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car