According to the following article:

"Even non-bootable disks can spread a boot sector infection when they are accessed"

Is it possible to access the data in a USB drive without executing the machine code in its boot records, which may be infected?

What if we have a rule that all our external drives are always partitioned with just one partition? Then there's no need for boot machine code, is there?

never thought linux kernel executes something from USB/etc "on connect"...
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upd: i also never thought some executable code can be stored in boot records...

It's the terrible way they designed it, back in the 80's the bios did not know anything about partitions and neither does it now, the bios or its substitute just executes the machine code in the master boot record that implements the partitioning functionality, which may therefore not be the standard of up to 4 partitions (3 primaries, one extended) but something else completely different, or even a virus.

Boot records in partitions also contain executable machine code, useful if they are bootable. Hopefully this code does not get executed in our case a USB drive being hotplugged. But it may well be, cause otherwise how can boot sector viruses exist.