[GENERAL] vacuumdb --analyze-only scans all pages?

Hello,

PostgreSQl  9.6.1: after a pg_dump/restore procedure it scans all pages 
(at least for some of the tables, analyze-only switch is specified).

I would expect that only the sample rows are scanned.

"log_details": scanned 2133350 of 2133350 pages

vacuumdb --analyze-only --all --verbose
INFO:  analyzing "public.log"
INFO:  "log": scanned 30000 of 30851 pages, containing 3599899 live rows 
and 0 dead rows; 30000 rows in sample, 3702016 estimated total rows
INFO:  analyzing "public.log_details"
INFO:  "log_details": scanned 2133350 of 2133350 pages, containing 
334935843 live rows and 0 dead rows; 3000000 rows in sample, 334935843 
estimated total rows
INFO:  analyzing "public.log_details_str"
INFO:  "log_details_str": scanned 30000 of 521126 pages, containing 
3601451 live rows and 0 dead rows; 30000 rows in sample, 62560215 
estimated total rows

Any ideas why?

Thnx.

Ciao,

Gerhard