Hello Henry,
No, it is normal. It is due to the fact that the column names in the attribute table of a shapefile are limited to 10 characters each, so the command just shortens the column names to fit with this. If you want to get the entire column names, you can use another output format like geopackage:
ogr2ogr -f “GPKG” /{path}/parcels.gpkg PG:“host=localhost user=admin dbname=sen4cap password=sen2agri port=5432” -sql “SELECT * from decl_{site_name}_{year}”
Best regards,
Philippe