In a sense you're right - it's not an electron that jumps around, the electron is its quantum amplitude wavefunction. Until you measure it, that is what you need to calculate the details of and time evolution of and interactions with.
And there can be electron wavefunctions that are macroscopically distributed for sure.
But as the electron's eventual interaction shape is a point, and never more than one point (even if the wavefunction was a large drumbell shape before!) we can't say that the electron "grows thinner and larger" itself, we have to conclude that there is a thing called a wavefunction (or quantum amplitude) that evolves that is not a point, that can be used to predict where/when the single-point "full electron" interaction with something else might take place.
A quantum weak measurement is a measurement where the object you want to study is allowed to interact with a part of the detector that doesn't immediately reduce everything to a single point interaction. As you correctly note, it does change the shape of the wavefunction, but what you also need to know is that the wavefunction change is not of the electron and the detector-part by themselves - there is a combined wavefunction for the electron + detector-part pair now, with a distribution of amplitudes for their possible states.
It quickly gets intuitively messy but this is the core...
And there can be electron wavefunctions that are macroscopically distributed for sure.
But as the electron's eventual interaction shape is a point, and never more than one point (even if the wavefunction was a large drumbell shape before!) we can't say that the electron "grows thinner and larger" itself, we have to conclude that there is a thing called a wavefunction (or quantum amplitude) that evolves that is not a point, that can be used to predict where/when the single-point "full electron" interaction with something else might take place.
A quantum weak measurement is a measurement where the object you want to study is allowed to interact with a part of the detector that doesn't immediately reduce everything to a single point interaction. As you correctly note, it does change the shape of the wavefunction, but what you also need to know is that the wavefunction change is not of the electron and the detector-part by themselves - there is a combined wavefunction for the electron + detector-part pair now, with a distribution of amplitudes for their possible states.
It quickly gets intuitively messy but this is the core...