FYI, it is acceptable to shave pads a bit. Some pins are overly wide as well, so that a positive side fillet is somewhere between undesirable and impossible.
IPC-7351 is fine with slightly negative side fillet, and I haven't found problems doing this in practice.
Example: 0.5mm pitch, 0.25mm max pin width. Don't use 0.3mm pad width. That leaves 0.2mm space, of which 0.075mm on each side must go to copper-to-mask-opening clearance, due to the typical 0.075mm positioning error between copper and mask. That leaves 0.05mm for the actual mask web width, which is far too little. At that size, it won't work at all, or it will flake off during manufacture or assembly.
To get 0.075mm or better gap and web width, you need 0.225mm or more between pad edges. If you use 0.25mm pads, a web width of 0.1mm is quite manufacturable.
Most 0.5 and 0.65mm pitch components have pin widths equal to half the pitch, so this is straightforward.
I've seen a lot of VSSOP/MSOP parts where the leads are wider. In that case, it's your call whether to size the pads accordingly, or keep them around half pitch. At least the ones that are 0.65mm pitch, the pad gap can still be comparable to 0.5mm-pitch, half-width dimensions.
I've been told by one assembler, that they only look for one good solder fillet, preferably toe where it's easily inspected. Sides don't matter, and heel is optional. More is fine of course, but it's good to know the minimums.
Tim