One other thing is, is there more one way to play B major? Why are there different fingerings for just the B major chord? For example:
A major chord is a triad of three notes: the root note, the major third, and the perfect fifth. For the B major chord, the notes are B, D♯, and F♯.
Any combination of those three notes on your strings will form a B major chord. If the lowest note played is a B, the chord is in root position; otherwise, the chord is an inversion, which changes the character of the sound. When playing solo ukulele, this will depend partly on whether you use high G or low G tuning.
Which fingering you use in practice depends on what other chords or notes you play, as it’s easier to transition between some fingerings. Different neck positions and fingerings can also produce subtle differences in tone. Skilled listeners will be able to tell the difference between chord voicings, but they are all still “B major” chords.
Each of the examples in your fingering chart show exactly which frets to play on each string to create those three notes. The fret numbers are on the left side of the chart, and the notes to play are shown above the strings. For example, in the first fingering, you play B on the fourth fret of the G string, D♯ on the third fret of the C string, F♯ on the second fret of the E string, and B on the second fret of the A string. In the very last fingering, you play on the F♯, B, and D# on the 11th frets, and B on the 14th fret. These two fingerings will play the chord in different octaves, with different inversions, but they are both still B major chords.
You ask 'Why are there different fingerings JUST for the B chord'. If that's what you meant, there are just as many fingerings for MOST chords. The examples shown are different mixes of the 3 notes needed for a major chord. If you look carefully,the 2nd and the 3rd diagrams actually have the same 3 notes on the same 3 strings on the same 3 frets (exactly as a guitar,top 4 strings, but in a different key),but obviously the fingerings will be different. Check others and you will see similar pattern copying.
There are (as I remember) 7 different position of a chord in a guitar (or ukulele). Which consist the triad notes (for minor 1-b3-5 and 1-3-5 for major).
If you ask about B major chord, which all major chord have 1-3-5 rule, which in B major it will be: B-D#-F#. All of your images shown those three notes.
In your images, they're the same three notes, B-D#-F#, but in different position or(/and) different octave.