Inventory sync on the part of Shopify and eBay is almost instant as and when there's a change on the channel in question. This is because Shopify and eBay has a way of notifying us the moment there's a change on your store. This sync with Shopify and eBay involves orders and all the other product details.
Unfortunately, Etsy doesn't have anything of that sort, so we sync inventory at a 30 minutes interval. This 30 minutes interval sync for the other channels is only on the part of orders so that the change in quantity can be updated on the other channels that the product is listed on.
For manual changes in other product details on these channels (Etsy), merchants will need to import their products again on SynCommerce for those details to be updated on the other channels the product is listed on.