I might be mistaken, but it seems to me this paper discusses unintended
ways of obtaining the IP addresses of clients involved in transactions on
the core Bitcoin network.
Tor was mentioned only insofar as it might be one's first thought of how to
mitigate this risk, yet Bitcoin over Tor has its own problems that prevent
this from being effective.
But the primary "issues" mentioned in the paper are regarding a Bitcoin
node in default operation, no?

"In their new study, researchers at the Laboratory of Algorithmics,
Cryptology and Security of the University of Luxembourg have shown that
Bitcoin does not protect user's IP address and that it can be linked to the
user's transactions in real-time."

"The basic idea behind these findings is that Bitcoin entry nodes, to which
the user's computer connects in order to make a transaction, form a unique
identifier for the duration of user's session. This unique pattern can be
linked to a user's IP address. Moreover, transactions made during one
session, even those made via unrelated pseudonyms, can be linked together.
With this method, hackers can reveal up to 60 percent of the IP addresses
behind the transactions made over the Bitcoin network."

"'This Bitcoin network analysis combined with previous research on
transaction flows shows that the level of anonymity in the Bitcoin network
is quite low,' explains Dr. Alex Biryukov."

M