Vue中曾经出现的<render>是做什么的?

在学习Vue源码时偶然发现，有个processRender(element)，该函数定义为

// 2.0.0-alpha.1 src/compiler/parser/index.js 125行
function processRender(el) {
    if (el.tag === 'render') {
        el.render = true
        el.renderMethod = el.attrsMap[':method'] || el.attrsMap['v-bind:method']
        el.renderArgs = el.attrsMap[':args'] || el.attrsMap['v-bind:args']
        
        if (process.env.NODE_ENV !== 'production') {
            if (el.attrsMap.method) {
                warn('<render> method should use a dynamic binding, e.g. `:method="..."`.')
            }
            else if (!el.renderMethod) {
                warn('method attribute is required on <render>.')
            }
            if (el.attrsMap.args) {
                warn('<render> args should use a dynamic binding, e.g. `:args="..."`.')
            }
        }
    }
}

里面有<render>标签，但在2.0.0-alpha.5中取消了这个标签和processRender的处理。2.0.0-alpha.5的Release Notes中说

The <render> tag is removed in favor of stateless functional components.

想知道这个标签是干嘛用的，百度谷歌都搜不到一点信息。它和无状态的函数式组件又有什么关系？