I've only got personal, empirical data to go on, based on my driving a Mk
5 Escort and a Mk2 Mondeo.If you remove the battery, the ECU takes half an hour or so to re-learn all of its settings. Until this point, performance is down, and the engine tends to stall.
If you drive it in a spirited manner, it seems to "get used" to it, which leads to "poor" economy, not particularly good low speed driving, but fun high speed driving.
Similarly, if you drive like a pensioner, it gets used to it, and needs a bit of thrashing before you can drive in the manner of paragraph above.
Just my 2ps worth.
Pete.