I was hoping to get more information about weighted sleeping bags. I was always under the impression that these are not advised as safe for sleep but I have come across a brand who believe that they are meeting safe sleep guidelines with their weighted sleeping bag product. Can you please clarify if these are considered safe? and if there are specific features which make some brands safer than others?

Red Nose have no specific information about these products in relation to safety.
Weighted blankets & sleeping bags are fairly new to the market for babies/toddlers.
Not sure of the marketing rationale for these products, but think there is some association with settling, sleeping longer but most significantly reducing the ability of baby to roll.
This, of course carries risks, as rolling is a normal development stage & a safe environment for rolling to occur should be provided, rather than trying to stop it.

I notice on some advertising mentions the weights applying (gentle) pressure to the chest.??

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
Using lightweight blankets/sleeping bag is important to allow baby to move freely, particularly when starting to roll & to reduce the risk of overheating.

Maybe that particular company is suggesting that they meet “safe sleeping guidelines” by encouraging baby to sleep on back & that the weighted sleeping bag makes it more difficult for baby to roll.
Red Nose recognises that rolling is a normal development stage & babies sleep environment should be as safe as possible to allow baby to roll well…...ie in a cot with firm mattress & cease swaddling/wrapping. Always place baby on back for sleep.