Not quite. IIRC, having seen all the BBC News24 broadcasts of the press conferences through into Saturday, Sir Ian announced during one of the two Friday broadcasts that the initial forensic examinations at Aldgate and Edgeware Road suggested that the bombs were located at floor level in doorwells. And drew the inference that this implied that they had probably been left there rather than being carried by suicide bombers.
By the Saturday, the new understanding of the chain of events was that the three Tube explosions were very close together (the Edgeware Road one originally having been thought to be about 20-30 minutes after the first two, which in turn had been thought to be 5-10 minutes apart). That suggested the use of timers.
Then on Monday night came the breakthrough with the identities and the CCTV footage.
The Mirror’s speculation was reasonably clever, given what was known by the end of Thursday, but was never formally suggested by the police in public. (There was always the problem of how, if people were leaving bombs on trains using Kings Cross as a hub, two made it through several stops, but one never got to the next stop. Various scenarios were suggested, but IMHO none were very satisfactory.)
It’s to the Met’s credit in the last week that when they have drawn conclusions in public they have described their reasons for reaching them. It makes it much easier to understand why they have revised some conclusions when one can see how much weight to accord to the different lines of evidence as they develop from day to day.