[agentultra]

> Perhaps that isn't a problem

It really isn't a problem. AFAIK there isn't a run-time performance to using cross-implementation libraries. If you're building an application you probably don't even need to worry about supporting multiple implementations and can write to the available extensions directly. Fortunately the spec left us with a highly-extensible "programmable programming language." Libraries fill the gaps between implementations which push the gap as technology changes. The core is just the bedrock to build upon.