Why do you use dot to access array item instead of brackets

[gritsenkob]

In templates You use dot(.) to access array item(e.g. "firstSegments.MSH.10")
On the other hand liquid documetation says that you can use square brackets to access array item(e.g. "firstSegments.MSH[10]")
link to liquid documentation: https://shopify.github.io/liquid/basics/types/#array
I`m confused a little bit