These two instances of the "sandal" actually suggest the same thing - the removal of the sandal was actually a recognition of the loss of property and inheritance rights. This was true whether it was done by the aggrieved widow or by the man himself.
There are several references to this in the OT such as Ps 60:8, 108:9. Note the comments of Benson:
Deuteronomy 25:9-10. Loose his shoe — As a sign of his resignation of
all his right to the woman, and to her husband’s inheritance; for as
the shoe was a sign of one’s power and right, (Psalm 60:8; Psalm
108:9,) so the parting with the shoe was a token of the alienation of
such right; and as a note of infamy, to signify that by this
disingenuous action he was unworthy to be among free men, and fit to
be reduced to the condition of the meanest servants, who used to go
barefoot, Isaiah 20:2; Isaiah 20:4. His name — That is, his person,
and his posterity also. So it was a lasting blot.
The Cambridge commentary offers similar comments:
and strip his sandal from off his foot] ‘As one occupied land by
treading on it, the shoe became the symbol of taking possession (Psalm
60:8; Psalm 108:9); when a man renounced property to another, he drew
off and gave him his shoe. So among the ancient Germans the taking off
of the shoe was a symbol for giving up property and heritable rights,
and with the delivery of the shoe or the throwing of it away goods
were conveyed to another. Similarly among Hindoos and Arabs,
Burckhardt, Bed. 91’ (abridged from Knobel). Cp. the Bedawee form of
divorce: ‘She was my slipper, I cast her off’ (W. R. Smith, Kinship,
etc., 269). That the right was a duty, which should not be renounced,
is marked by the woman’s drawing off the sandal, and spitting in the
face of the recusant (Numbers 12:14, Job 30:10, Isaiah 50:6). Sandal,
Heb. na‘al, Ar. na‘l.
See also the comments on Deut 25:9 from Barnes, and Matthew Poole.