From the days when I was a service technician for a route operator:

When the coin door is opened, inserting coins does not increment the electronic bookkeeping coin meters for each coin chute. This way, when a service tech or coin collector for the route operator clears a coin jam, they test the coin chutes running several coins through to make sure credits are placed onto the credit counter of the game.

Some route operators paid their commission split via what the meters indicate. Without the Memory Protect feature, every "test coin" used by the person servicing the game needed to be recorded on a card/notepad in the game so those phantom credits would not be used to pay the commission split to the location owner.

There still was a notebook carried by the collectors listing what the meters indicated the previous collection.

Ironically, we only used a computer (back in the office) to pay splits (actually commissions) for the cigarette machines we had on the route. Checks were mailed.

The "soft meters" in the pins were used to verify that the coin mechs were't being stringed, or a hole was drilled in the cabinet to activate the coin switches, locks being picked etc.

Video games still had hard meters like EM pins. When I worked on the route, All EM's were in storage already and we pulled 20 or so per year and sold them for home buyers at Christmas time. I recall one video game manufacturer had the same sort of memory protect switch that deactivated the hard coin meter with the door open. Not sure if it was Stern (Berzerk, Scramble etc.) or Cinematronics (Dragon's Lair, Space Ace) or maybe Gottlieb Q-Bert, M*A*C*H*3{choke}....

Most ops counted coins in front of a location representative. The business was mainly cash. Im sure all income was properly reported for tax purposes on both sides. Some operators did it by sending checks or taking paper cash on the next trip. Or the funds were used to pay down "Loans" given to the location. Not that there were loan sharks in the amusement, music & vending businesses at one time.

As far as your Laser Ball experiment, maybe my memory is failing and I'm full of shit, who knows? All I remember is that we didn't have to mark "service credits" on games with the non-interlocking switches on the coin doors. Maybe there is a setting with those simple Williams option settings? Dip switches were so nice on Bally, Gottlieb and Stern games.

Bally had the service credit function on 7 digit display SS games. On those we just cut power and held the coin lockout bar to verify coin jams were fixed. But then you had to verify the coin switches were working.
We're going back about 40 years now.