Regarding whether or not the reveal that the Disassembly Drones were sent by Cyn rather than JC Jensen, as I see it's far from an ass pull, there was a fair amount of foreshadowing for it.
In episode 2, Uzi discovers that the radio in the Disassembly Drone's landing pod was destroyed, and N questions who and how J was receiving orders from if not the company through the radio. V also asks Uzi if she has any proof for "her backstory, which makes her kind seem oh so innocent", further implying everything is not as it seems with the situation.
In episode 5, we see disassembly drone parts in Cyn's basement, well before they were supposed to have existed. Additionally, we're shown in the zombie drones tape the correct procedure to disassemble a worker drone according, which involves disconnecting and destroying their AI core. None of the Disassembly Drones did this, the spire of corpses they build is in fact exactly the opposite of the correct method for AI disposal.
Particularly the bit about the landing pod radio was a strong sign that something was amiss, and the sight of disassembly drone parts in Cyn's basement pretty much seals the deal.
Regarding whether or not the reveal that the Disassembly Drones were sent by Cyn rather than JC Jensen, as I see it's far from an ass pull, there was a fair amount of foreshadowing for it.
Particularly the bit about the landing pod radio was a strong sign that something was amiss, and the sight of disassembly drone parts in Cyn's basement pretty much seals the deal.