They actually explain that in greater detail in the middle of the paper. According to McLeay, Radia and Thomas (2014):
Money can also be destroyed through the issuance of
long-term debt and equity instruments by banks. In addition
to deposits, banks hold other liabilities on their balance sheets.
Banks manage their liabilities to ensure that they have at least
some capital and longer-term debt liabilities to mitigate
certain risks and meet regulatory requirements. Because these
‘non-deposit’ liabilities represent longer-term investments in
the banking system by households and companies, they
cannot be exchanged for currency as easily as bank deposits,
and therefore increase the resilience of the bank. When banks
issue these longer-term debt and equity instruments to
non-bank financial companies, those companies pay for them
with bank deposits. That reduces the amount of deposit, or
money, liabilities on the banking sector’s balance sheet and
increases their non-deposit liabilities.
In the 10y bond example above I would say money was not destroyed because that 10y bond would be likely liquid enough to count as broad money (although if you would just want to look at narrower measures it would). However, some non-traditional long term debt that is very illiquid would qualify even with broad measures of money.