SQL MERGE and temporal tables overpopulated history table

I have a table I created as a temporal table using a command as follows:

create table darren/tstp
(prod char(35) not null with default,
desc char(50) not null with default,
ChgUsr varchar(18) implicitly hidden generated always as (USER),
Start_TS timestamp(12) implicitly hidden not null generated always as row begin,
End_TS timestamp(12) implicitly hidden not null generated always as row end,
TS_ID timestamp(12) implicitly hidden generated always as transaction start id,
period system_time (start_ts, end_ts)
);

ALTER TABLE TSTP ADD VERSIONING USE HISTORY TABLE TSTP_H;

If I run an SQL MERGE similar to the following, where the QTEMP table has the same data as the target table, I get a history table record every time the merge is run. Is there an option I'm missing to basically say, don't update the table if none of the fields are different? I realize I could perhaps write a compare for each field, but sometimes a file might have hundreds of fields, so, I was hoping for something a little less laborious. An SQL update does the same thing (a history record for every non-update), but, I looked at the MERGE, hoping it was a little more intelligent, so, if there is something different that could be done with the UPDATE, that might be interesting too.

merge into darren/tstp a using
(select * from QTEMP/tstp) b
on a.PROD=b.PROD
when matched then update set
desc=b.desc
when not matched then insert
(prod,desc)
values(
b. prod,
b. desc)