Are commercial bought weighted sleep sacks safe? (for example- https://www.nestedbean.com/pages/zen-sleepwear )

Red Nose recommends using a sleeping bag that has appropriate size neck & arms holes & no hood.
This is to prevent overheating & head/face being covered.
Any bedding should be of light weight material.

A good way to avoid face covering is to use a safe baby sleeping bag (one with fitted neck, armholes or sleeves and no hood). If using bedclothes rather than a sleeping bag, it is the best to use layers of lightweight blankets that can be added or removed easily according to the room temperature and which can be firmly tucked in.
https://rednose.org.au/article/protecting-baby-from-overheating-during-sleep

There is very little evidence to support the use of weighted bedding for babies, & Red Nose recommends the use of appropriately sized sleeping bags (that meet Australian Standards) & light weight blankets if necessary.

Product Safety Australia develops & monitors safety standards in Australia.
The standards for sleepwear is predominantly related to the flammability of the type of material being used.
https://www.productsafety.gov.au/standards/nightwear-for-children