/proc/{pid}/wchan contains the function name, not its address.
In this example he's just printing the syscall that his example process is running.
The calls to strace and gdb are disjoint, he's cut out a lot of stuff here, probably why its confusing. In the commands he's used strace would dump all the syscall details to the console and GDB would just attach to the process and enter its normal console (presumably hes determined hes stuck in a loop so hes just using disassemble).
In this example he's just printing the syscall that his example process is running.
The calls to strace and gdb are disjoint, he's cut out a lot of stuff here, probably why its confusing. In the commands he's used strace would dump all the syscall details to the console and GDB would just attach to the process and enter its normal console (presumably hes determined hes stuck in a loop so hes just using disassemble).