Importing tiles with raster2pgsql

Hi all,

I have a dataset with several hundred tiles (GeoTIFFs) that make up a
digital terrain model.
Each tile is 0.5d x 0.5d.

I tried to load these GeoTIFFs to PostGIS with:

$ raster2pgsql -s 32631 -I -M -F -C -t auto -d -l 2,4,8,16,32 tif/*.tif (1)

The data was loaded, but when viewing in QGIS, it looked like jagged lines
with areas of white overlain by pieces of neighboring tiles, etc.
This didn't look right.
I also noticed that for each tif, the constraints were printed.
I expected this to be done once, after the last tile was loaded.

I then created a virtual raster with gdalbuildvrt:

$ gdalbuildvrt merge.vrt tif/*.tif (2)

And then used raster2pgsql to load in the vrt:

$ raster2pgsql -s 32631 -I -M -F -C -t auto -d -l 2,4,8,16,32 merge.vrt |
psql (3)

The data was loaded, and looked good in QGIS.

Shouldn't commands (1) and (3) give the same results, or am I
misunderstanding?

Best, Andreas