Question: I am using Office Version 2206 (Build 15330.20230), the current version. When I am searching for an email it shows a message that maybe not all results are shown and that it is still indexing 127279 emails, many more emails than I have recieved since the issue occured. When I search for something it only shows results that more than a year old.

This problem occurs only since a couple of days, possibly since the last update from July 06.

Answer: 
Having 2ⁿ bit registers, allows bits in the registers to be addressed with an integer number of bits:

Addressing a bit in an 8 bit register will need 3 bits. Addressing a bit in a 16 bit register will need 4 bits. But, addressing a bit in a 12 bit register will need 3.58… bits. You would have to round it up to 4, thus wasting ≈0.4 of a bit.

Example
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* Immediate shift: the shift distance is stored in the instruction.
* Immediate read bit: reads a bit for a register, the bit number is specified in the instruction.
* Reading or writing a bit from a large memory field: Mask (bit wise and) to get upper bits of the address and use these as the byte address, mask (bit wise and) to get lower bits of the address and use these as the bit offset.

We don't always use registers to specify the bit. We often use immediate addressing (the address is in the instruction). Even arm does this, and it does not have immediate addressing (at byte level). When we have the address in a register, then we are often dealing with more than 32 bits, so have to mask the address to get the byte number and the bit number. This only works because of the power of 2.
Generally, processors are referred to as x-bit, where x is the width of the data bus.

In rough terms, increasing the data bus size offers primarily speed as a reward...twice the bits, twice the data access speed. This is the ideal; some inefficiencies are involved (e.g., fetching 1 byte still takes 1 cycle on a 32-bit system, same as fetching 4 bytes).

As ctrl-alt-delor points out, there are some logistical advantages to stick with a bus width of 2\*\*N. The only restriction of following this pattern is that you have to double the width every time you introduce a wider architecture, giving a max access speed increase of 2.

And in the end, it's hard to justify a new architecture if it's not at least twice as fast as the old one.

Note that low end microcontrollers offer many exceptions to this rule, and the properties of audio and human perception have made 12 bits a popular width for DSPs.