How does the November 2018 PH errata change the usage of multiclass spell slots to cast spells?

Question

The Player's Handbook, pg. 114, once read (in the wizard's Spellcasting feature description):

The Wizard table shows how many spell slots you have to cast your spells of 1st level and higher.

The November 2018 PH errata states:

[New] Preparing and Casting Spells (p. 114). In the first sentence, “your spells” is now “your wizard spells.”

Now that section reads:

The Wizard table shows how many spell slots you have to cast your wizard spells of 1st level and higher.

The errata also applies the same change to classes and archetypes with the Spellcasting class feature.

A single-classed wizard won't notice the difference, but I wonder if this change means multiclassing means spell slots gained from multiclassing to cleric, for instance, cannot be used to cast wizard spells that is not in cleric spell list?

How does this errata change how multiclass spell slots work?

Answer 1

It doesn't

Multiclassing has its own set of rules that define what spell slots you have, and this overrides the spell slots mentioned in the wizard class section.

The errata you mention was added (I assume) to avoid you using those slots for spells gained from some other place such as a feat or racial feature.

Answer 2

The errata doesn't change anything for multiclassing

The rules for multiclassing override those of the individual classes:

Once you have the Spellcasting feature from more than one class, use the rules below. If you multiclass but have the Spellcasting feature from only one class, you follow the rules as described in that class.

So any rules that are described in the multiclassing part of these rules simply replace the ones from single class casters.

Note that the multiclassing rules explicitly give classes the ability to use slots in a shared way and this is the rule you should follow instead of the one listed with your class:

If you have more than one spellcasting class, this table might give you spell slots of a level that is higher than the spells you know or can prepare. You can use those slots, but only to cast your lower-level spells.

So this errata change, being a change to a section of the rules explicitly replaced by the multiclassing rules, has no effect.