I have no issue when printing from the iPhone, but when using the MBP it just doesn't fit the picture to the print. Looks almost like it's trying to put the picture in the middle of the paper that's a much larger size, so half of the print is just white border while the lower quarter of the paper has some of the picture on it. Using Big Sur 11.6
MacOS apps ultimately use the MacOS print engine. The difference is in what they “tell it” to print. If the image is centered but the edges all get cropped off, then when in the print dialog box, go to the advanced settings. It sounds like you have got the scaling set to 100% rather than fit to paper OR, the print settings are telling it you are using A4/legal paper size not a 4x6 - you should be able to tell the printer that. Note though that the benefit of using Photoshop or LR for example is that you get greater control over what to print at the cost of complexity to set it up.
By clicking the Presets box you should be able to access the print page that allows you to specify quality of print, paper size and scale.
If the options for paper size, scaling etc are not there, then you may need to install newer driver software.