When combined with Black Wall & Dominance from Dust, the skeletal mage duration keeps on extending even if the golem is already gone.
In addition to a description of the bug you are reporting, please provide:
Device Type: PC
Device Model: Desktop
Device Operating System: Windows 10
Diablo Immortal App Version: 3.0.3.2250616
This doesnt sound like a bug it sounds intended for a way to have mages not on a timer. The whole update centers around that (IE unlimited golem). You can only have 6 summons max so it should keep killing skeletons for the mages. In fact this may be a great way to take advantage of the old skele attack speed build again that buffs attack speed for the party when a skele dies. You have to sacrifice the vuln golem offhand to do this and lightning skeles, so its just a build variant. The reason it continues forever is likely that the smaller golems count as another golem to reset the timer.
I just tested and its meant to create unlimited mages, you also dont need split golem for it. Its intended.