If you need this feature, you could check if you have (or can obtain) a USB hub with a USB-C connector on one side, and multiple USB-A ports on the other?
In the past I tested with a fairly cheap hub, connected to a less powerful USB-C charger (the one delivered with the original 2016 Google Pixel). It charged multiple devices successfully. The charging speed for each device was lower than if that one had been connected directly to the charger alone, but not too horrible.
Note, I don’t have any projector yet, and can’t be certain if it works with that charger! You might want to ask someone else to test before you consider purchasing a hub.
Adding another port will require two separate voltages to be output as well, making the adapter more complicated, but sure there are adapters like that. My Comkia adapter (as mentioned here Dimensions of and markings on included AC adapter?) is very similar in size to the Philips one and does have one USB-A port in addition to the USB-C PD port. That has been my travel charger of choice, but it only provides up to 3A output at the 15V level, so not quite up to the Philips adapter power.
Well you could also extend USB functionality of the projector itself, using the ports of the PPM to support higher output current on both the USB-A and the USB-C port, basically turning it into a proper powerbank, that way you don’t have to complicate the charging adapter itself.
There are all these 100’s of new chargers getting around, just another purchase, but I reckon of Phillips could “whack” a couple more ports on the included charger it would be a big win. I mean surely the existing charger is already 90% of the way/cost towards one of these things:
In actual componentry costs, it can’t be much more aye?