A new curriculum was introduced in 2014. Tests reflecting that curriculum were introduced in 2016. Since then the time allowed for the Key Stage 2 reading assessment has not changed. The test framework for the English reading test places a limit on the number of words that can be included in the texts and this limit has not been breached.
Assessments go through a rigorous test development process lasting three years. Thorough trialling of the materials, with the texts in the combinations they will appear in a final test, allows test developers to ensure the reading booklets are suitable and that the standard is maintained.