I had not thought of it that way, but you’re right. It is a bit like Twitter’s 140 characters. The goal will be 150 words, but the intention, as always, will be 150 words of quality. That’s quite a different matter.
There are only so many characters that you can fit into a space of 140 characters, but the number of words you can fit into a space of 150 words–and the variability possible within such a space–leaves substantially more room for expression (or lack thereof).