Ah, ha; a vinyl tweak that worked. ’-)
The shape of the groove is determined by the cutting lathe stylus so there is a specific stylus alignment that best traces that cut. The alignment of the stylus in the groove is determined by a combination of several parameters, such as VTF, SRA, azimuth, and even anti-skate.
The thing about tonearms and cartridges is that if you make a change in one parameter, like VTF, it affects other parameters, like SRA and can also affect the signal generator in the cartridge. So when you do make a change, you have to consider the other ways you could achieve the same alignment in the groove or could affect the generator in the cartridge. You added VTF, which caused the cantilever to take on more force and change angle, which caused the stylus to ride in the groove at a different SRA. But it may have also changed the alignment of the cantilever in the signal generator of the cartridge.
For example, instead of adding VTF, try keeping the VTF the same, but lower the tonearm base so the cartridge tilts back just a bit and realigns the angle of stylus (SRA) in the groove, similar to the SRA you’d get by adding VTF. You may or may not hear the same difference in sound.
You could also change the angle of the cantilever in the cartridge body by adding VTF but keep the SRA the same by raising the tonearm base. By having the same VTF for different SRA alignments, you’ll be hearing more of the affect of SRA. If you don’t hear much difference, then the additional VTF is probably affecting the cartridge’s signal generator and producing the difference in sound.
That’s the fun of this hobby.