The 1.19.60 changelog states:

• Orbs spawned within the same block will merge and combine XP values until orb limit is reached

However, this does not occur in-game.

Steps to reproduce

1. Load XP Orbs Do Not Merge.mcworld. This world has a scoreboard and command blocks set up to spawn and count xp orb entities.
2. Flip the lever.

Expected result

The count of xp orb entities goes up steadily while they are spawning and periodicaly goes down as they merge.

Observed result

The count of xp orb entities goes up steadily and goes down only when they despawn after 5 minutes.

Note that if you stand close enough to the glass cage the orbs will appear to combine into one visually, but this is only because client-side xp orbs have no collision and do not sync with server-side xp orbs (see MCPE-11181). If you relog (MCPE-150723) or break one of the glass blocks on the ground and stand where the xp orbs move toward you very slowly, the client-side visual orbs will separate again.