PLCs – LR parsers and ambiguous and non-deterministic grammars

The dragon book says:

An ambiguous grammar can never be LR.

And then right away, he says:

For example, consider the pending grammar-else:

begin {align} stmt rightarrow & textbf {if} expr textbf {then} stmt \ & | textbf {if} expr textbf {then} stmt textbf {else} stmt \ & | textbf {other} end {align}

If we have an offset reduce the analyzer in configuration

$$begin {matrix} STACKING & ENTRY \ … textbf {if} expr textbf {then} stmt & textbf {else …} end {matrix}$$

we can not say if $$textbf {if} expr textbf {then} stmt$$ is the handle, no matter what appears below the pile. Here, there is a gap that reduces conflict. According to the following $$textbf {else}$$** on the entry, it might be ok to reduce $$textbf {if} expr textbf {then} stmt$$, or it might be ok to pass $$textbf {else}$$ and then look for another $$stmt$$
to complete the alternative $$textbf {if} expr textbf {then} stmt textbf {else} stmt$$.

My question is quite simple. The author starts by saying facts about "ambiguous" grammar, then he gives an example of a problem with the same prefix of the right sides of two productions (for example, the non-deterministic grammar), but without any relation with the Ambiguity of the grammar.

Am I right? Also what does it mean? LR grammar can not work with both: non-deterministic and ambiguous grammars?