There is only one value a kg could be in that example, everything else is constant. The question I think you're trying to ask is "why 6.62607015×10−34 instead of some other simpler value" and the answer is a bit longer.
Original 1 kg was the mass of a cubic decimeter of water at 4 C at 1 ATM. Why a cubic decimeter at 4 C? Water is densest at 4 C and a cubic decimeter of it is a weight that people can work with on a day-to-day scale. Unfortunately this was a bit hard to measure so they made the IPK (international prototype kilogram) which was a lump of metal. Fast forward 100 years and the lump of metal proved to be too unreliable for modern standards as it kept losing very small amounts of mass, also it Earth's gravity isn't even so it requires you average it out and then calculate the local offset and a whole bunch of other weird things that can mean a microgram or two. This is inconvenient but we still needed a way to say "1 usefull measurement of mass" but unfortunately in the universe 1 Planck's constant is far too small to ever use daily. Thankfully it has become easier to accurately measure Planck's constant against the IPK so now we have solidified 1 kg to be exactly what we measured.
The nice thing is 1 kg will forever be the same thing now and is easy to measure to extraordinary accuracy. The downside I think you're asking about is 1 kg by itself isn't some significant relation of the physical world, it's just a useful-in-daily-life multiple of mass as defined by Planck's constant.
Original 1 kg was the mass of a cubic decimeter of water at 4 C at 1 ATM. Why a cubic decimeter at 4 C? Water is densest at 4 C and a cubic decimeter of it is a weight that people can work with on a day-to-day scale. Unfortunately this was a bit hard to measure so they made the IPK (international prototype kilogram) which was a lump of metal. Fast forward 100 years and the lump of metal proved to be too unreliable for modern standards as it kept losing very small amounts of mass, also it Earth's gravity isn't even so it requires you average it out and then calculate the local offset and a whole bunch of other weird things that can mean a microgram or two. This is inconvenient but we still needed a way to say "1 usefull measurement of mass" but unfortunately in the universe 1 Planck's constant is far too small to ever use daily. Thankfully it has become easier to accurately measure Planck's constant against the IPK so now we have solidified 1 kg to be exactly what we measured.
The nice thing is 1 kg will forever be the same thing now and is easy to measure to extraordinary accuracy. The downside I think you're asking about is 1 kg by itself isn't some significant relation of the physical world, it's just a useful-in-daily-life multiple of mass as defined by Planck's constant.