"It looks like it exhausts at TDC but intakes at BDC. Is it sucking
vacuum all the way down?"

The animation only has a few frames so timing is not precisely represented.

It is a two-sroke engine. The exhaust valve opens shortly before BDC and
before the scavenging ports are uncovered.

Since it is a two-stroke engine there is no intake stroke as in a
four-stroke engine.

"Intake" occurs when the piston uncovers scavenging ports around the
cylinder wall shortly before BDC. Since at this point scavenging air
pressure is greater than cylinder pressure the remaining exhaust gases
are pushed out the open exhaust valve. The valve closes shortly after
the piston begins moving upward and compression begins for another power
stroke.

Rick