I think you're missing the point...
No 999 call was ever made. The initial incident was made to a local police station.
The situation at the SOC wasn't exactly clear, let alone at the HQIR.
For a number of hours isn't wasn't even known how many people were in the building, let alone alive or dead. It was supposed that there would be 5, but not known.
It was also unclear if there was a hostage situation or not.
It was also unclear if entry could be gained easily or not.
It was also unclear if Sheila was efficient in weapons handling.
It was also unclear if the Police could safely overpower Sheila without subsequent injury or loss of life.
Over time, more and more became apparent, but this took over 4 hours to ascertain.
During this period a number of conflicting reports were made (I believe quite genuinely), and were logged. The process of logging would also log 'mistakes' as were reported. e.g. Two bodies in the kitchen, one male, one female.
IF (and it's a huge IF), HQIR were told 2 people in the kitchen (at some stage), then told (one male found on entry), then told '5 people total found' then SOMEONE at HQIR DID do some maths - that is irrefutable - it's right there in black and white as '3 further bodies'.
My point is:
Either nobody at HQIR asked for clarification, or they missed / misunderstood 'one (male) body found in kitchen' or they simply knew of two bodies already, were told of the final (5) count and wrote the entry '3 further bodies found'.
Now, according to virtually all other evidence, the entry team distinctly counted 1 body in the kitchen and TWO in the Bamber's bedroom (Sheila and June), followed by two kids in their shared bedroom.
So you tell me, either the entry team lied. Or the entry team got all confused, or the HQIR team got all confused.
Whichever it was, none support your assertion that the police were capable. At least one element wasn't.
The only way '3 further' can be counted is based on the 3 in the kitchen. Since all others were reported in pairs, so '2 further' or '4 further' would work, but '3' can ONLY work if one believed two were in the kitchen. HQIR got it wrong, or the policeman reporting what HQIR had said got it wrong. - same result, wrong.
I personally believe it's an entirely plausible human error and not highly significant, but in writing ambiguous log entries one creates difficulty for people coming along later trying to interpret what happened.
How can '3 futher bodies' NOT be interpret as finding 2, then 3 further (which didn't happen according to conventional wisdom)?