Hi.
Yes, sequencing comes with its own problems. I only read a bit about the process so I'm not very well versed in the whole undertaking. mollisia does sequencing afaik, maybe he can tell you more about the interpretation.
I think in general it's not the worst idea to build a tree of your sequence and some close matches to see how it turns out and if any database entries are likely mismatched. You could try it with this, but don't ask me in depth about it - I only saved the page some time ago in case I ever did sequence something myself. Haven't needed it yet.
Assuming that the tree above is correct, then for example
KY693966 (X. rubellus) is also actually H. engelii and just misnamed.
The Unite entries are not in the tree above but:
UDB000444 is named in the UNITE taxon name: Xerocomellus chrysenteron (as Xerocomus communis) - maybe they view(ed) X. chrysenteron as the same species as H. engelii.
UDB000446 shows up as Xerocomus communis
UDB000445 shows up as Xerocomus communis
UDB000447 shows up as Xerocomus communis
And X. communis is just an old name for H. engelii. So to me everything points to the fact, that Pablo was right again.,
I'm not sure why you get X. chrysenteron in your matches.
About the cap color - the guy who build the tree above sequenced a bright red capped Hortiboletus and it turned out to be H. engelii. By macro alone I'd have called this H. rubellus...
And I read somewhere that H. rubellus can be brown-capped as well.
Xerocomoids are fun...
LG.