The normalisation process undertaken by Thomson Reuters analysts is based on reported company disclosure, albeit with their own methodology for how to interpret that disclosure. See here for details of that methodology.
As the level of disclosure in company accounts is often more limited in quarterly/interim accounts, it is possible that the level of normalisation adjustment in each quarter may be lower.
In these situations, Reuters adjust for unusual items in the annual report but can not do the same in the interims as the items were not reported. As the phasing is uncertain, Reuters elect to not adjust interim earnings at all rather than to estimate the adjustment.
For this reason, the annual normalised EPS figure will usually be more reliable than the quarterly numbers.