SELECT FOR UPDATE locks whole table

We have the following query:

SELECT certificate_id
INTO TEMP TABLE x_certs
FROM certificate
WHERE cert_status = 0 AND
certificate_id BETWEEN 1111 AND 2222 AND
client_id IN (1, 2, 3)
ORDER BY certificate_id
FOR UPDATE;

Is there any reason that this query should lock the entire certificate table?
Is there something strange because of the IN clause or because it is going
into a temporary table? This is a production server running 7.2.2 so perhaps
it is fixed in 7.3.

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