> My question was then, whether there is something that I have missed...

probably not. You can move the test into the match if you want of
course:

<xsl:template match="A" mode="two">
  <xsl:if test="not(preceding-sibling::node()[1][self::A])">2</xsl:if>
</xsl:template>

can be written

<xsl:template match="A" mode="two"/>

<xsl:template match="A[not(preceding-sibling::node()[1][self::A])]" mode="two">2</xsl:template>

If you prefer.

David

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