MCU crystal oscillator PCB layout confusion

[shadewind]

I'm laying out a board with an STM32F302C8 MCU and am currently looking at the ST Micro application note regarding crystal oscillators:
https://www.st.com/content/ccc/resource/technical/document/application_note/c6/eb/5e/11/e3/69/43/eb/CD00221665.pdf/files/CD00221665.pdf/jcr:content/translations/en.CD00221665.pdf

I've also looked into the equivalent Atmel (Microchip) app note and there are some commonalities that I don't quite understand as well as some differences that confuse me:
http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-8128-Best-Practices-for-the-PCB-Layout-of-Oscillators_ApplicationNote_AVR186.pdf

I was hoping someone could shine some light on some of these points:

• Both recommend a local ground plane only connected at the MCU pin. Since this is a four layer board, I've just made a split in the ground plane that is a snip that goes to the closest MCU ground pin and connected it to this ground plane through a via (screenshot attached) and it seems to be approximately how the STM app note is doing it. Is this correct? Also, I've never done anything like this before and not really had any problems so I'm wondering, how important is this really? I'm assuming that the reason is two-fold, to prevent the EMI from radiating out from the oscillator into the application ground plane but also to prevent digital noise from the ground plane radiating in and bothering the osciallator?
• Both app notes show crystal traces running through the load caps on the way to the crystal, how important is this? By running the traces directly to the crystal and then the caps, the trace length between the MCU and the crystal would be shorter.
• Microchip recommends grounding the crystal while ST Micro recommends not doing so. Datasheet for my ABM3B crystal says "GND" on the shield pads so it seems like it was actually made to be grounded but I don't know. It seems to be that it would be wise to shield emissions from the crystal by shunt the shield to ground.
• Both recommend guard traces around the crystal but I don't really have space for it and I don't see most people bother with it. How much does this matter?

Thanks in advance.