Indeed, and, with cut or awk, you can still merge these via paste to output of bcftools query, which is still very useful to use to extract tag information that is embedded in INFO or FORMAT:
paste \
<(bcftools view test.bcf | \
awk '!/^#/ {print $1":"$2":"$4":"$5}') \
<(bcftools query --samples 2610,2661,6313,6318 -f '%CHROM\t%POS\t%REF\t%ALT\t%DP\t[%AD\t]\n' test.bcf) \
| head -10
1:65797:T:C 1 65797 T C 5012 . . . .
1:65841:T:G 1 65841 T G 3234 . . . .
1:65851:C:T 1 65851 C T 3271 . . . .
1:65872:T:G 1 65872 T G 32370 236,39 . . 205,47
1:65918:C:T 1 65918 C T 8629 . . . 232,0
1:65974:A:G 1 65974 A G 7623 . . . .
1:65999:G:C 1 65999 G C 1767 . . . .
1:66162:A:T 1 66162 A T 805 1,1 3,1 . 1,2
1:69270:A:G 1 69270 A G 1064 . . . .
1:69428:T:G 1 69428 T G 870 . . . .