apex – SOQL on quotes showing weird behaviour

I have enabled quotes without opportunities in my org. I created a formula field test__c on quote having value opportunity.name.

[SELECT Id, test__c FROM Quote WHERE opportunityid = null] this gives me no results on developer console whereas
[SELECT Id FROM Quote WHERE opportunityid = null] returns all the records.

Both queries should give me same results ideally with test__c field values.

I found one documentation – help.salesforce.com/s/articleView?id=sales.cpq_quotes_without_opportunities.htm&type=5 which says

The quote page layout can’t contain formulas or lookups to formulas that refer to the fields on the Opportunities object.

Not sure if this is due to same reason. This is happening only on quote object.