NO!!! This is wrong, where did you pick this up from? If the equipment has a charged up DC-blocking cap, it will discharge into the front-end and kill it.
Doesn't it have input protection for that?
Summarizing, the BM789s is DC-coupled as far as the hardware and DMM IC, and there's a HPF from the true-RMS DSP section if Brymen is using it verses the MCU doing the math with raw A/D samples.
So I believe it can be saturated with DC on any ACV measurements if it can't auto-range up, and the F/W needs a check to see of if it lets you know this is happening.
I looked at the usual dozen multimeter schematics, the ones incorporating a DC-blocking cap for ACV. Maybe others can contribute.
None of the asian design multimeters I can find are using a DC-blocking cap, except the BM869s.
The "protection circuit" is needed to clamp down to the IC level, the CMOS switches downstream of the HV protection MOV's. Interestingly, the AC path does not include anything like our usual diode-connected transistors etc. which end up on the DC/ohms path. AC protection is by large series resistance, 87V is 10MEG and 34401a is 1MEG so the cap discharge is low current, enough for an IC's substrate diodes to handle. But the voltage is still high for whatever you are probing, not sure what a mosfet does with HV on the gate at low current, for a long time. ESD is short duration and 10X and the voltage at 1/20 to 1/200 the capacitance.
Interestingly ACV the 87V moves the 9.99MEG after the cap, so it's a 10MEG AC impedance and very high (leakage) DC resistance.
So using a single-resistor HV probe with the DMM on ACV would charge to a clamped couple kV DC-component and not be a good experience.
Oscilloscopes have larger blocking cap (up to 22X) and lower impedances for the bandwidth, some using relays/switches or maybe solid-state AC/DC coupling switching. The cap discharge is brutal there maybe 15mJ across the switch and goodbye JFET if you short the probe's input. 2235a rated 400VDC goes 0.022uF down to 1,000pF +ve discharge through 70R to the JFET, minus a 10X probe. It all depends on the moves you make while the cap has a HV charge.
As far as providing a make/model/schematic a showman could use, awareness of the charged cap is more important than damaging something. I treat it like a grenade- a high risk measurement (AC ripple/signal on HV DC) across the board.