Apple Platform Security document:

All Mac portables with the Apple T2 Security Chip feature a hardware disconnect that ensures the microphone is disabled whenever the lid is closed. On the 13-inch MacBook Pro and MacBook Air computers with the T2 chip, and on the 15-inch MacBook Pro portables from 2019 or later, this disconnect is implemented in hardware alone. The disconnect prevents any software—even with root or kernel privileges in macOS, and even the software on the T2 chip—from engaging the microphone when the lid is closed. (The camera is not disconnected in hardware, because its field of view is completely obstructed with the lid closed.)

That’s the Mac side. On the iPad:

iPad models beginning in 2020 also feature the hardware microphone disconnect. When an MFI compliant case (including those sold by Apple) is attached to the iPad and closed, the microphone is disconnected in hardware, preventing microphone audio data being made available to any software—even with root or kernel privileges in iPadOS or in case the firmware is compromised.

The culture of camera and mic access on the Mac and iPad are very different. On my Mac, when the camera is in use, I see a light. And, as the note states, when the lid is closed, the camera is blocked.

Hardware disconnect does prevent the mic from working when the iPad case is closed. But what if I use my iPad without a case? And what about the camera without a case? There’s no hardware disconnect to rely on. Instead, Apple requires apps to ask for permission to access the camera and microphone.

Seemingly foolproof, but no.