WRONG!
http://www.toutsurlegaznaturel.com/pdf/SAFETY.pdf
Depending on how long the gas has leaked, the pressure at which it leaks (bigger leak, higher pressure) house will fill quicker. There are what are known as Explosive / flammable limits Air to Gas mix too high, won't light, mix too low won't light, just right it will light off. Just because the news is reporting "Explosions", does not mean that all the homes were not "Gas Fed Fires". which headline sells / is more dramatic?
Gas does not explode, it burns. A house that has filled with gas is withing the Explosive / Flammable Limits meets an ignition source, light turning on, fridge compressor etc. will explode.