This, of course, lines up with previous rumors that have been swirling around the Galaxy S10 in the past few weeks. The code for the app explicitly shows that there is an in-display fingerprint sensor, and there is now support in the latest version of the app. Since Samsung Pay is only available on Samsung devices (and really only a few at that), it would have to be one of the Galaxy S10 models. Though it is still not confirmed which one in particular will get this in-display sensor.
What makes it harder to decipher which particular variant will have the in-display fingerprint sensor, is the fact that all of them share the "beyond" codename, which is how the device is identified in the code. So this could be the Galaxy S10, Galaxy S10+ or the Galaxy S10 E. Though, judging on various rumors, the Galaxy S10 E would likely not be the one to get this, seeing as it is aimed at a more low-end/mid-range segment.
Since Qualcomm announced its new Ultrasonic Fingerprint Sensor last December, it has been rumored that Samsung was the first customer for this new sensor. Qualcomm said that a partner would be launching it in the next few months. But as usual, Qualcomm did not specify the name of that partner. Though many had assumed it would be Samsung, due to their close relationship, and rumors were already surfacing of Samsung using an in-display sensor.
With the Ultrasonic sensor that Samsung is rumored to be using, users would be able to unlock their phone with their finger, even if it is dirty, has oil on it, or is shrivled after doing dishes, taking a shower, etc. Which makes it a whole lot more useful than the other in-display fingerprint sensors that are on the market today. Which are mostly slow and often times, inaccurate.
Samsung is expected to debut the Galaxy S10 in a few weeks, on February 20. The company has already sent out invites to the February 20 San Francisco/London dual-event with a big "10" on the invitation. Essentially confirming the product that is going to be "Unpacked" at the event. This is earlier than usual for Samsung. It usually announces it the day before Mobile World Congress - which would be February 24 this year - and in Barcelona. There's no real word as to why Samsung is doing it a bit early this year, perhaps to get even more coverage, seeing as it is the tenth anniversary of the Galaxy S.
Currently, there are at least three variants of the Galaxy S10 rumored, with the standard regular and plus models, and then a "Galaxy S10 E" which is going to be a more mid-range option. But Samsung is also working on a 5G smartphone that will be coming to all four of the US carriers later this year. Which many believe will also be a Galaxy S10 model. This means that there could be more Galaxy S10 models than there has been in the past few years (you'd have to go back to the Galaxy S and Galaxy S2 days for this many variants).