struct buf_queue_head still existing in 5.x/6.x ?

Can someone explain why in both 5.x and 6.x, we still have
"struct buf_queue_head" defined in sys/buf.h ?

I thought it was replaced by 'struct bio_queue_head' almost
everywhere - as a matter of fact, the definitioni in sys/buf.h
seems to be a duplicate of the one for struct bio_queue_head
in sys/bio.h (mutatis mutandis), and a grep gives only a handful
of usages:

> cd /usr/HEAD_050628/src/sys
> grep -r buf_queue_head *
dev/aac/aac_compat.h:#define bio_queue_head                    buf_queue_head
dev/amr/amr_compat.h:# define bio_queue_head                   buf_queue_head
dev/mlx/mlx_compat.h:typedef struct buf_queue_head             mlx_bioq;
dev/twe/twe_compat.h:typedef struct buf_queue_head             twe_bioq;
sys/buf.h:struct buf_queue_head {
> cd /usr/R5_050628/src/sys
> grep -r buf_queue_head *
dev/aac/aac_compat.h:#define bio_queue_head                    buf_queue_head
dev/amr/amr_compat.h:# define bio_queue_head                   buf_queue_head
dev/mlx/mlx_compat.h:typedef struct buf_queue_head             mlx_bioq;
dev/twe/twe_compat.h:typedef struct buf_queue_head             twe_bioq;
sys/buf.h:struct buf_queue_head {


	thanks
	luigi