Yes, and I can also confirm that this time the United Kingdom's release also has music missing, there is a disclaimer printed on the back of the box, although the Disks are single sided as per usual here in the UK. The price was set very low for this release in the UK, a good 30% cheaper than the past 3 seasons upon release, presumably Season 4 was cheaper because of the missing music.
I bought the region 1 edition of season 4, and there are songs missing, but they are very few (compared to previous seasons). If you take a look at Al's place, you'll notice their list for missing music in season 4 is very wrong. Only the following songs are missing :
THE LEAP BACK "Is You Is or Is You Ain't My Baby?" Performed by: B.B. King
PLAY BALL "Traveling Man" Performed by: Ricky Nelson
RUNNING FOR HONOR "Easier Said Than Done" Performed by: The Essex
TEMPTATION EYES "I Want to Know What Love Is" Performed by: Foreigner