China’s first-quarter data dump on Friday provided some encouraging signs about the condition of the world’s second-largest economy in the first three months of the year. But a closer look at some of the figures -- from property to pork -- raises questions about how healthy and sustainable the latest pickup in growth momentum is.

Property: Investment in property, which accounted for a huge portion of economic activity during the boom years, is back. The property market’s contribution to first-quarter’s economic growth was...