pg_stat_progress_vacuum empty when running vacuum full

Hi all,
I'm running 11.5 and I'm monitoring pg_stat_progress_vacuum every 2
seconds, while doing from another connection per-table VACUUMs. Every
vacuum last 30 or more seconds, so I was expecting to see a record
within pg_stat_progress_vacuum, but nothing appears if the vacuum is
full. I suspect this is due to vacuum full performing a side-by-side
table rewriting, rather than in-place actions against the original
table, but I'm not sure if this is real reason or if I'm missing
something.

Thanks,
Luca