Looks like they are a service provider and combine multiple domains on one cert. Were you thinking they just were not cleaning up obsolete TXT values?
Example: crt.sh | 10823447789
Update: Also see related thread with call-out to staff: DNS-01 challenge fails since unbound 1.18. TXT records can be fetch using unbound 1.16 but not 1.18 1.19 - #17 by petercooperjr