He's kind of right though, although not very polite about it ;p, you missed the lights. With that amount of 1000w I bet his lower bud is heavier than most 600 growers mid bud and his mid bud as dense as their top. I would sooner agree with his number than try to call him a liar simply by looking at a pic that does not translate density very well and it also seemed you gave a number assuming 600w lights. 10 days worth of trimming would also possibly back that up as he trimming a lot of the more time consuming lower stuff.
What ever the case why automatically assume somebody is a liar, not just you, the others too. All I can read into that type of attitude is projection of your own limitations.
If he is a liar, so be it. He got the attention either way ;p.