It’s fine as long as you don’t plan on using your DJI warranty while the drone is still covered.
As for the third party batteries you're considering, it's hard to say how they'll perform compared to DJI's. I wouldn't assume all batteries from...
The website looks legit, and the delivery time is much better than Alli Express. Please let us know how this order goes. If the battery arrives when promised and lives up to the specs, I will be tempted to try this new alternative to Ali...
You have raised a very important point about securing the battery for each flight. I learned from others in this forum that all batteries used by the Mavic 1 Pro and Mavic 2 Pro MUST be secured with zip ties, and this rule applies to the stock...