Below is an exact “safest” WHERE clause tailored to your schema and your distribution results. It is conservative: it deletes only real user timeline posts, skips system-generated events, skips pinned/sticked/promoted, and only targets active/visible items.

What we will delete (whitelist)

From your distribution table, the only thing that represents the “native Timeline post” objects is:

• type = 'timeline_common_post' (action is blank / NULL in your data)

We will not touch:

• comment (65639) — these are comment events
• timeline_common_repost (3130) — reposts
• module-generated “added” events: bx_posts, bx_photos, bx_videos, bx_ads, bx_groups, bx_polls
• profile changes: bx_persons actions

Safest WHERE clause

Use this in your cleanup query:

WHERE `type` = 'timeline_common_post'
  AND (`action` IS NULL OR `action` = '')
  AND `date` < ?
  AND `system` = 0
  AND `status` = 'active'
  AND `status_admin` = 'active'
  AND `active` = 1
  AND `pinned` = 0
  AND `sticked` = 0
  AND `promoted` = 0
  AND `owner_id` > 0
  AND `object_id` > 0

Full query drop-in (recommended)

Replace your current selection block with:

$eventIds = $db->getColumn("
    SELECT `id`
    FROM `bx_timeline_events`
    WHERE `type` = 'timeline_common_post'
      AND (`action` IS NULL OR `action` = '')
      AND `date` < ?
      AND `system` = 0
      AND `status` = 'active'
      AND `status_admin` = 'active'
      AND `active` = 1
      AND `pinned` = 0
      AND `sticked` = 0
      AND `promoted` = 0
      AND `owner_id` > 0
      AND `object_id` > 0
    ORDER BY `date` ASC
    LIMIT ?
", [$cutoff, $batch]);

Why this is the safest

• Type/action whitelist ensures you only delete the Timeline’s own “common post” items, not module activity events or comments/reposts.
• system = 0 prevents removal of “system” entries.
• status/status_admin/active ensure you only remove content that is currently treated as active/visible by UNA.
• pinned/sticked/promoted = 0 avoids deleting highlighted content.
• owner_id/object_id > 0 avoids orphan/system rows.

One optional safety improvement (recommended)

Run a preview query in phpMyAdmin before going live:

SELECT `id`, `owner_id`, `date`, `type`, `action`, `system`, `status`, `status_admin`,
       `active`, `pinned`, `sticked`, `promoted`
FROM `bx_timeline_events`
WHERE `type` = 'timeline_common_post'
  AND (`action` IS NULL OR `action` = '')
  AND `date` < UNIX_TIMESTAMP(DATE_SUB(NOW(), INTERVAL 60 DAY))
  AND `system` = 0
  AND `status` = 'active'
  AND `status_admin` = 'active'
  AND `active` = 1
  AND `pinned` = 0
  AND `sticked` = 0
  AND `promoted` = 0
ORDER BY `date` ASC
LIMIT 50;

If those 50 rows look exactly like “old timeline posts you truly want gone,” you are good to proceed.

If you want to also delete reposts safely later, we can add a second pass with type='timeline_common_repost' but I would keep that separate from the first run.

You're very kind.