MacBook – Detect a connected USB-C charger cable that is not charging

Yes - the SMC reset should resolve any temporary issues with the hardware not sensing the charge adapter. It's even called out in this KB article by Apple as something SMC reset can potentially address:

http://support.apple.com/kb/ht3964

Once you ruled out SMC needing to be reset, you should get the Mac in to a repair shop or do what they would do to isolate the hardware failure:

• test your adapter with another computer
• test your computer with another adapter
• test your computer with another OS (last resort - SMC and the charging behavior you report can be tested with the OS powered off and only the firmware / SMC regulating the LED color and charge state based on the data it can collect which is faulty in your case)

Once they have isolated the failure (likely to your computer), they would open it and inspect for any corrosion or damage on the logic board and charging circuitry and the either swap and test the magsafe board or the battery or the logic board itself based on experience and the hardware service manual for your model.

A good Multimeter is fantastic - I use one all the time - however it's not clear from your question just how you're using a Multimeter to take your measurements?

Considering we're talking about a fairly recent model MacBook Pro, I suspect you haven't opened it up to take these measurements. Instead, I recommend you download and install coconutBattery¹. It provides a whole heap of information that you'll find useful, and from memory includes both Discharging and Charging measurements in watts!

Some thoughts

It's not clear from your question why you're investigating all this? Unless you've actually got a problem you're trying to address, using the charger that came with your MBP should be perfectly fine. Also, in relation to you not finding any articles that indicate what a normal USB PD output is relative to the devices they connect to, that's because PD stands for Power Delivery and most of these devices are just designed to allow the power travel through them from the charger to the device being charged.

In other words, you can use a hub with a USB-C PD port with a 2017 MacBook Pro and also use it with a HP Elitebook and the voltage/watts will differ, depending on the device and charger.

¹ I am not affiliated with coconutBattery in any way.