Out of character: I am choosing to interpret that "Bob wins ties" as not using the standard tie breakers. As in, if both hands are straight flushes, normally the higher card wins, as a course of 'breaking the tie'. But in this case no high card comparison is made and Bob wins a straight flush / straight flush matchup. Same with royal flush, straight, and flush. I don't know why, but in my mind it made sense that a four-of-a-kind, three-of-a-kind, pair, full house, etc still compare high card. Alice's 4 Aces still beats Bob's 4 Queens as if there never were a tie to begin with. This might not have been the intention, but custom rules make sense with the following flavor text:
Alice and Bob are playing Face-Up Poker. For the first game,
Alice chooses a Royal Flush and Bob chooses a Royal Flush. They both keep their hands.
According to the Poker Hand Tie Rules, they split the pot. Being Alice and Bob, it takes them 3 more games of exactly repeated cards to learn that neither of them are getting anywhere. They thus agree that high card or high suit shall determine the winner in the case of a tie.
Following this new rule and the previous strategy, it takes Bob 5 more games for him to realize he's not getting anywhere, no matter which lower suit ace he chooses. The rules are thus amended, on threat of Bob playing "never ever again", whereupon high card and high suit are totally ignored and all ties yield Bob's winning.
Play thus proceeds, with Alice realizing from past experience she must prevent a Royal Flush:
Alice takes 4 aces and a king, to prevent Bob's Royal Flush.
Bob must settle for a straight flush.
Using one of her aces, Alice is free to take a royal flush, and she wins.
4AK, SF -> RF, SF = Alice
Next game, Bob also realizes he must
thwart Alice's royal flush attempt.
When Alice takes 4 aces and a king, Bob takes a straight of a king, queen, jack, ten and nine, all of different suits.
Alice cannot go "straight" (pun intended) for a royal flush, but she naively thinks her 4 of a kind to be winning and so she keeps it.
Bob beats the four aces with a straight flush.
4AK, KQJ109 -> 4AK, SF = Bob
Realizing what she did, in the next game Alice
takes 4 aces and a king again.
Bob takes king through nine of different suits.
Then Alice goes "straight" for the straight flush with the highest card possible, a queen (even though this was irrelevant under the rules, she likes queens).
Bob also takes a straight flush, and wins the tie without high card comparison.
4AK, KQJ109 -> SF_Q, SF = Bob
On a losing streak, Alice cannot continue with her past method of preventing a royal flush, so for the next game Alice decides to use Bob's own tactic against him.
Alice takes ace through ten, all of different suits!
Bob cannot make a royal flush, so Bob takes a straight flush.
Alice is able to take a royal flush and wins, because Bob, having been unable to obtain a royal flush the first round, is still not magically able to make a royal flush.
AKQJ10, SF -> RF, SF = Alice
Just when Alice thinks she's finally turned the tables, she
takes ace through ten, all of different suits.
Bob cannot make a royal flush, but this time he does the same to Alice, taking a different set of ace through ten, all of different different suits.
Without the possibility of her own royal flush, Alice upgrades her straight to a straight flush using lower cards.
Bob also has a straight flush laid out in front of him somewhere on the table, and he wins the tie without high card comparison.
AKQJ10, AKQJ10 -> SF, SF = Bob
In the end
Alice makes several more attempts.
Try as Alice might, she cannot both block a royal flush and beat a straight flush from Bob.
Bob always wins either flat out or by virtue of the special rules established.
Having determined the answer, the Alice, Bob and Charlie (yes, Charlie) personalities retreat back into the subconscious, allowing Daniel to emerge and write this down.