All of these rules are just rules of thumb.
The "rule" is that your Power Delivery Network (PDN) needs to have low-enough impedance to function properly. High parallel capacitance and low series inductance/resistance. Longer leads increases inductance and resistance so closer is preferred.
But for even 100MHz designs, you're well under the size where 100mil or 0805 would cause any serious problem.
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So the "secret" is that all faster designs (100MHz to 300MHz) have substantial on-package capacitance.
Take a look at this design, which I admit is Microchip/Atmel MCU, but its running at 300MHz and not just the relatively low 133MHz of the RP2040.
https://lcamtuf.coredump.cx/bob-the-cat/
Those are LARGE 1206 1uF capacitors. Which is actually scary to me because we're not looking at tight 100nF decoupling caps anymore but instead substantially relying upon "on-package" capacitance.
Still, it shows that lcamtuf was confident in this 300MHz processor handling far-away 1206 capacitors, showing how much wiggle room we have in practice in these designs.
You shouldn't worry about 100mil of movement of 0805 caps on a 133MHz design. After all, there are real designs that are closer to 500 mil that use 1206 caps on a 300MHz MCU.
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I'm honestly scared for lcamtuf here and would never design a board like this. But I'm really not worried about 0805 caps on relatively low speed 100MHz (or even 133MHz) MCUs. Especially if you're properly "teaming" them up so that their resistances are paralleled and inductances are paralleled. (Notice that lcamtuf's 300MHz design doesn't even have the 10x recommended parallel 100nF capacitors close to any of the pins!! He's really stretching the specs)
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But yeah, my personal preference is majority of 0805s and 0603s for the "close" decoupling capacitors. I know there's plenty of wiggle room here (even if I'm not as aggressive as lcamtuf's designs).
If you're using PCBA from another shop, I guess its all "free" to you to use 0402s or whatever they got loaded in their chip-shooters. So might as well take your free pre-loaded resistors. But if I'm assembling a board myself, I definitely prefer the larger size.