Are unique indexes used to verifiy unicity on insert?

Question

PostgreSQL 13.5, PostGIS 3.2, Windows server 2012

Here is the table I have created

CREATE TABLE IF NOT EXISTS activite.unobs_rest
(
gid integer NOT NULL,
numunobs character varying(20) COLLATE pg_catalog."default",
typunobs character varying(20) COLLATE pg_catalog."default",
interpret character varying(60) COLLATE pg_catalog."default",
datedebut bigint,
datefin integer,
gidoperef integer NOT NULL,
geom geometry(Geometry,2154),
periode character varying(50) COLLATE pg_catalog."default",
CONSTRAINT pk_gid PRIMARY KEY (gid)
)

The table contains 412859 rows.
Here are the partial indexes :

create unique index idx_2col_geom_numunobs on unobs_rest (MD5(st_asbinary(geom)), numunobs) where numunobs is not null;
create unique index idx_1col_geom on unobs_rest (MD5(st_asbinary(geom))) where numunobs is null;    

Indexes are supposed to prevent duplicates when inserting a row with the same geom&numunobs or the same geom&numunobs IS NULL of an existing row.

But this doesn't work.

After reading Postgres partial index on IS NULL not working, I have updated the statistics, even if I don't run select query :

analyze activite.unobs_rest (geom)
analyze activite.unobs_rest (numunobs)

But again, I can copy and paste an existing row without any problem, which I don't want.

question Is there a way to know if indexes are used when I try to insert a row in unobs_rest ?