[2] explains this by the capacity effect of the passive (overhang) anode (which is approx 5% of the total anode):
Hence, the observed capacity increase (or decrease) over the first few cycles depends on the long-term storage conditions prior to the test (temperature and State-of-charge).
I'm not entirely convinced by this theory because it seems to me that it should change the discharge capacity only during the first cycle, but it continues to increase over several cycles.
Anode overhang effects can increase measured cell capacity after rest at 100% SoC.
In any case, this effect is one of the examples of the tendency that Cell data mining, analysis, and modelling are greatly complicated by factors that are not essential to cell electrochemistry.
The reverse process is Cell capacity fade.
See also:
"Data-driven prediction of battery cycle life before capacity degradation" (2019)
[2] "Systematic aging of commercial LiFePO4jGraphite cylindrical cellsincluding a theory explaining rise of capacity during aging" (2017)
https://s3-us-west-2.amazonaws.com/secure.notion-static.com/b6def513-34be-401d-af35-750249645099/lewerenz2017.pdf