Determining whether something is worth reading doesn't require a good summary, just one that contains enough relevant snippets to give a decent indication.
The opportunity cost of "missing out" on reading a page you're unsure enough about to want a summary of is not likely to be high, and similarly it doesn't matter much if you end up reading a few paragraphs before you realise you were misled.
There are very few tasks where we absolutely must have accurate information all the time.
