1. Smartmatic software is used by other companies too.
2. This change could happen before votes are being reported.

EDIT:

I do know that PA does use Dominion (They had a scheduled testimony today which Dominion bailed out of).

https://greatgameindia.com/philadelphia-dominion-foreign-interference/

However this:

https://thedailycoin.org/2020/11/20/philadelphia-previously-rejected-dominion-voting-systems-for-fear-of-foreign-interference-who-knew/

says the following:

The Philadelphia bid was ultimately awarded to Election Systems & Software (ES&S). Even this company contained a system that runs directly against the advisories put forth by the Pennsylvania Blue Ribbon Commission on Election Security. The Blue-Ribbon Commission decided that ES&S puts Pennsylvania’s elections at risk “because of its voting methods and machinery.” The Blue-Ribbon Commission also warned about the use of bar code and QR machines because they are not readable by humans. This method caused widespread reports of voter suppression during the 2018 midterms in Georgia.

Also it's possible that all these machines send their result to a common place for them to get "calculated" before getting reported.

1. Smartmatic software is used by other companies too.
2. This change could happen before votes are being reported.