The problem with that is you'd need to match to the soldered-on memory specs to gain all performance benefits, as opposed to just buying a matched set and plugging it in yourself. You're also stuck with whatever highest common clock speed all the RAM would support instead of whatever the maximum the memory controller would allow.

I'm afraid the reality is that finding a laptop without at least some of the memory soldered on is increasingly difficult. Some T series Thinkpads prior to 2019 did but that ship has sailed and there were no AMD T series Thinkpads prior to May of 2019. So installing a matched set is not an option in the T495.

One of the great things about the T series of Thinkpads is that access to replace memory and storage is quick and easy unlike many modern laptops. Another advantage is that they are heavily documented and have a vibrant community around them. This means determining the memory specs needed to match the soldered-on memory is a rather trivial exercise. If any one is looking to purchase a T495 matching the soldered-on memory means using a PC4-19200 CL17 unbuffered non-ECC sodimm. You should be able to find a good brand module for about 1/5th of what Lenovo wants to factory install the additional memory.