No, this is not true. Heat created by microorganisms during composting kills weed seeds and disease-causing organisms.
Temperatures of compost piles routinely reach 65°C (149°F) for consecutive days; high enough to kill weed seeds. To test this, a study was done in which cookie sheets filled with compost were placed in an office window and watered to see if anything would germinate. Nothing ever did.
Compost is a great growing medium. If any weed seeds are blown onto your garden after you have added the compost, weeds are certainly bound to germinate. By their design, weed seeds flourish in disturbed soil, especially ones with nutrient rich compost added to it.