current() within a key element's @use

Shouldn't these
    <xsl:key name="keyUsingCurrent"   match="color" use="current()/@id"/>
    <xsl:key name="keyWithoutCurrent" match="color" use="@id"/>
produce the same set of keys?

With this XML
   <t>
      <color id="b">blue</color>
      <color id="r">red</color>
   </t>

    <xsl:key name="keyUsingCurrent"   match="color" use="current()/@id"/>
    <xsl:key name="keyWithoutCurrent" match="color" use="@id"/>

    <xsl:template match="/">
        (1):<xsl:value-of select="key('keyUsingCurrent', 'b')"/>
        (2):<xsl:value-of select="key('keyUsingCurrent', 'r')"/>

        (1):<xsl:value-of select="key('keyWithoutCurrent', 'b')"/>
        (2):<xsl:value-of select="key('keyWithoutCurrent', 'r')"/>
    </xsl:template>

        (1):blue
        (2):red

        (1):blue
        (2):red

        (1):
        (2):

        (1):blue
        (2):red