perhaps because that's installing from a store, not sideloading? however poor (security-wise) the offering may be, you're still using the intended install flow
in this sense i do actually agree about the misuse of 'sideloading' - the planned change would not impact just sideloading, but also 'third party' stores
That the term "sideloading" has normalized treating this as a special case is a problem.
It's unlikely the terminology can be rolled back at this point, but occasionally reflecting on this is useful.