Then sifted (∞,1)-colimits preserve finite products.
This is (Lurie, lemma 220.127.116.11).
Every filtered (∞,1)-category is sifted.
This appears as (Lurie, prop. 18.104.22.168).
In a category of commutative monoids in a symmetric monoidal -category, sifted colimits are computed as sifted colimits in the underlying -category.
See commutative monoid in a symmetric monoidal (∞,1)-category for details.
Section 5.5.8 of