It looks like the Wikipedia page could stand to be updated. If you look at the accumulated global-mean-sea-level data for all the altimetry missions (there are data for 9 of them listed), you can see that the values determined by different missions operating at the same time are consistent within about a 1.5 cm range, and all the missions together show a fairly steady 3.3 mm/yr sea level rise. Since that value is smaller than the variation between measurements across missions, and since the date range of each mission varies, it is natural that the rate of change seen in the data for a single mission might vary as opposed to another mission, but taken together the satellite data give a consistent picture.
The quoted text from the Wikipedia page, in any case, seems to exaggerate the difference between the cumulative rates measured by the specific missions it names. The referenced site gives 2.95 mm/year for Json-1, and 2.49 mm/year for Envisat.
Json-2 was active from 2008-2017 and showed a rate of 4.42 mm/year.
To sum up
- Cumulative satellite data provides no indication that mean-sea-level
rise is slowing down.
- Satellite sea-level data is noisy but
consistent enough to be useful, especially when combining data from
multiple missions across decades.