HP 1820 Static LACP Inqure

Hello, 

I want to confirm if this is possible as based on the reading I did, this should not be possible or I am understanding this incorrectly. 

I currently have one HP 1820 48G switch setup up and connecting to two core switches that are 1920S. 

Both of these cores switches are connected to one firewall. 

The HP 1820 48G I have configured port 47 and 48 LACP Static and connecting port 47 to one switch and port 48 to another switch (Just to test and see if this acually works) 

I am able to connect two seperate switches and have it load balance all traffic comming from the access switch to these two cores. 

Upon testing it does appear that this conifguration seems to work. I know LACP is suppose to be used between another switch, but it is standard practice to have it connected to 2 switches from on truck? 

I linked to the drawing for a better understanding on this. 

https://imgur.com/Nwc3Q4m

Thanks