I know chasers are bisexual because I'm a straight ciswoman who likes twinks and dick. Women are nice but I don't feel attracted to them.
And a lot of transwomen chasers call hot and breedable literally look and sound like cute twinks. Breast growth aside, most of the body reads as anime twink person. They do not read as natural women. But a chaser will still say that's straight and he wants to see her dick.
Exceptions are men who meet transwomen and just fully assumed they are dealing with a woman until they found out, that's straight. But chasers fetishize the maleness of a transwoman otherwise.