Jake Wood was on a break during this time (hence the appearance in June 2016, half way through the break), and the plan was always for him to return from the break which is why the duration is 2006-2021.

This is also consistent with the duration of other characters such as Stacey Slater, who didn’t physically appear for over a year (aside for a one-off appearance in October 2019) but we knew she was only on a break.

I get that, but surely due to the duration of the break, we can count it as a return?

The longest gap he had between appearances was 8 months, though. Changing his duration would make it inconsistent with other character pages such as Dot Branning, who also didn't appear for 8 months during a break in 2012 and, didn't return until 2013. Both actors were still on permanent contracts during their breaks, and never officially left the show.