Alchemists' Supplies can be infused using the Enhanced Arcane Focus infusion and can also benefit from the Alchemical Savant subclass feature. These effects stack.
An alchemist's supplies can indeed be infused using the enhanced arcane focus infusion. The alchemist's supplies can also benefit from the 'alchemical savant' subclass feature. Since both of these effects exist simultaneously and are not from identically named game sources they stack.
The reasons/justifications are listed below:
1.) A rod is listed as a scepter or just a heavy cylinder. Magic rods are typically made of metal, wood or bone. It's about 2-3 feet long, 1 inch thick and 2-5 pounds.
2.) Thus ONLY magic rods are defined as TYPICALLY made of metal wood or bone (Meaning NOT always).
3.) Alchemists' supplies include a glass stirring ROD (meaning it is a ROD made of glass).
4.) Tools Required States: that you must have a spellcasting focus - specifically thieves' tools or some kind of artisan's tool. It also states that after gaining the infuse item feature at 2nd level you can use ANY item bearing one of your infusions as a spellcasting focus.
5.) Infusing an Item states: you can touch a non-magical object and imbue it with one of your artificer infusions, turning it into a magical item. An infusion works on only certain types of objects, as specified in the infusions description. (i.e. ANY object of the specified type for the infusion).
6.) Enhanced Arcane Focus states: A rod, staff or wand (requires attunement).
7.) If the definition of a term is specified (which it is), then the use of that term refers to its specified definition.
Thus the glass stirring rod is indeed a ROD and has all the features of the predefined term rod, and is made of glass, an atypical but not invalid material. It is an alchemist tool, which is a type of artisan's tool, which can be used as a spellcasting focus for an artificers' spells and thus can benefit from the alchemical savant subclass feature. Since it is a rod, it can also be infused using the enhanced arcane focus infusion. Thus both effects are applied and since they are not duplicate game effects of the same name, they stack.
The entire premise of the infusion system is the imbuement of non-magical objects into magical objects and the description of rod states that MAGIC rods are TYPICALLY made of metal, wood or bone.
The term TYPICALLY means that rods can in fact, be made out of other materials. Since the normal process to create magical items is not being used to create artificer infused magical items, it is very reasonable that artificer infusions can be used on non-metal, non-wood and non-bone rods.
This is even further corroborated by the fact that even permanent magical rods are NOT strictly required to be made of metal, wood or bone.
Thus it makes even more sense that the glass stirring rod can be used for the enhanced arcane focus infusion.