Bug report: 'is_not_set' filter on People page returns people who have a value for the property

[slshults]

Bug Description

Please describe.

When filtering the People page by a property and using the is_not_set operator, the results include people who have a value for the property, though they should be excluded from the results.

HogQL captured (from the example in the repro steps below) in the browser console network tab shows:

WHERE or(equals(properties.subscription_plan, NULL), not(JSONHas(properties, 'subscription_plan')))

🤔

How to reproduce

This is a good project to repro on

1. On the people page, Add a filter for: subscription_plan is not set
2. Observe that persons with subscription_plan = free are included in the results

Expected: People with the property key present (regardless of value) should not appear.

Actual: People with actual values for the property are included in results.

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Additional context

From: https://posthoghelp.zendesk.com/agent/tickets/38942

Debug info

Session: https://us.posthog.com/project/sTMFPsFhdP1Ssg/replay/0199a0ea-72bd-73bc-a58d-24867686038a?t=3685
Admin: http://go/adminOrgUS/01917a47-db47-0000-7453-ced6e86fa8b4 (project ID 125931)