Can I connect pin 23 on the ADIS16495, to +VDD, like I could on the ADIS16485?
Yes, while the current datasheet specifies this as a “do not connect” pin, this pin is not connected to anything inside of the ADIS16495 package, so it is OK to leave this pin connected to +3.3V.
NOTE: For those who are not aware, the ADIS16375, ADIS16480, ADIS16485, ADIS16488, ADIS16488A all used pin 23 for the VDDRTC function, which required connection to +3.3V. The ADIS16490, ADIS16495 and ADIS16497 no longer offer the VDDRTC function, so connecting pin 23 to VDD (or a separate +3.3V supply) is no longer a requirement. For systems that already make this connection, application of +3.3V to pin 23 will not cause operational problems or damage to the ADIS16490, ADIS16495 or ADIS16497.