I apologize for messing with the correspondence (and for my bad English too), but I opened both jpegs and my Photoshop shows that they are both 300 ppi and both have the same pixel size, exactly the same size as the TIFF file. The difference is that they have different sizes in MB, only from that the files are processed differently (one of them seems more contrast).
Please note that you are confusing the terms ppi and dpi, they are not equal to each other and as long as you view the file on the monitor screen they have absolutely no meaning. I also work in the Agency and note the fact that 99% of people with whom I work do not understand the terms dpi and ppi and what this characteristic affects.
If agency refusing file 4000х3000px with 72ppi, but accepts it with 300ppi - they also doesn't know anything about dpi\ppi.
Sorry for using Google translate, hope you understand what i mean, you can also read something about ppi and dpi difference in good source.